Git 2.44-rc1

Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/.cirrus.yml b/.cirrus.yml
index 4860beb..77346a4 100644
--- a/.cirrus.yml
+++ b/.cirrus.yml
@@ -1,7 +1,7 @@
 env:
   CIRRUS_CLONE_DEPTH: 1
 
-freebsd_12_task:
+freebsd_task:
   env:
     GIT_PROVE_OPTS: "--timer --jobs 10"
     GIT_TEST_OPTS: "--no-chain-lint --no-bin-wrappers"
@@ -9,7 +9,7 @@
     DEFAULT_TEST_TARGET: prove
     DEVELOPER: 1
   freebsd_instance:
-    image_family: freebsd-12-3
+    image_family: freebsd-13-2
     memory: 2G
   install_script:
     pkg install -y gettext gmake perl5
@@ -19,4 +19,4 @@
   build_script:
     - su git -c gmake
   test_script:
-    - su git -c 'gmake test'
+    - su git -c 'gmake DEFAULT_UNIT_TEST_TARGET=unit-tests-prove test unit-tests'
diff --git a/.github/workflows/check-whitespace.yml b/.github/workflows/check-whitespace.yml
index a58e2dc..a241a63 100644
--- a/.github/workflows/check-whitespace.yml
+++ b/.github/workflows/check-whitespace.yml
@@ -19,7 +19,7 @@
   check-whitespace:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@v4
       with:
         fetch-depth: 0
 
diff --git a/.github/workflows/coverity.yml b/.github/workflows/coverity.yml
index e5532d3..53cf12f 100644
--- a/.github/workflows/coverity.yml
+++ b/.github/workflows/coverity.yml
@@ -38,7 +38,7 @@
       COVERITY_LANGUAGE: cxx
       COVERITY_PLATFORM: overridden-below
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - name: install minimal Git for Windows SDK
         if: contains(matrix.os, 'windows')
         uses: git-for-windows/setup-git-for-windows-sdk@v1
@@ -98,7 +98,7 @@
       # A cache miss will add ~30s to create, but a cache hit will save minutes.
       - name: restore the Coverity Build Tool
         id: cache
-        uses: actions/cache/restore@v3
+        uses: actions/cache/restore@v4
         with:
           path: ${{ runner.temp }}/cov-analysis
           key: cov-build-${{ env.COVERITY_LANGUAGE }}-${{ env.COVERITY_PLATFORM }}-${{ steps.lookup.outputs.hash }}
@@ -141,7 +141,7 @@
           esac
       - name: cache the Coverity Build Tool
         if: steps.cache.outputs.cache-hit != 'true'
-        uses: actions/cache/save@v3
+        uses: actions/cache/save@v4
         with:
           path: ${{ runner.temp }}/cov-analysis
           key: cov-build-${{ env.COVERITY_LANGUAGE }}-${{ env.COVERITY_PLATFORM }}-${{ steps.lookup.outputs.hash }}
diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index 9fdbd54..7bacb32 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -63,7 +63,7 @@
           echo "skip_concurrent=$skip_concurrent" >>$GITHUB_OUTPUT
       - name: skip if the commit or tree was already tested
         id: skip-if-redundant
-        uses: actions/github-script@v6
+        uses: actions/github-script@v7
         if: steps.check-ref.outputs.enabled == 'yes'
         with:
           github-token: ${{secrets.GITHUB_TOKEN}}
@@ -112,7 +112,7 @@
       group: windows-build-${{ github.ref }}
       cancel-in-progress: ${{ needs.ci-config.outputs.skip_concurrent == 'yes' }}
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@v4
     - uses: git-for-windows/setup-git-for-windows-sdk@v1
     - name: build
       shell: bash
@@ -123,7 +123,7 @@
     - name: zip up tracked files
       run: git archive -o artifacts/tracked.tar.gz HEAD
     - name: upload tracked files and build artifacts
-      uses: actions/upload-artifact@v3
+      uses: actions/upload-artifact@v4
       with:
         name: windows-artifacts
         path: artifacts
@@ -140,7 +140,7 @@
       cancel-in-progress: ${{ needs.ci-config.outputs.skip_concurrent == 'yes' }}
     steps:
     - name: download tracked files and build artifacts
-      uses: actions/download-artifact@v3
+      uses: actions/download-artifact@v4
       with:
         name: windows-artifacts
         path: ${{github.workspace}}
@@ -157,7 +157,7 @@
       run: ci/print-test-failures.sh
     - name: Upload failed tests' directories
       if: failure() && env.FAILED_TEST_ARTIFACTS != ''
-      uses: actions/upload-artifact@v3
+      uses: actions/upload-artifact@v4
       with:
         name: failed-tests-windows
         path: ${{env.FAILED_TEST_ARTIFACTS}}
@@ -173,10 +173,10 @@
       group: vs-build-${{ github.ref }}
       cancel-in-progress: ${{ needs.ci-config.outputs.skip_concurrent == 'yes' }}
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@v4
     - uses: git-for-windows/setup-git-for-windows-sdk@v1
     - name: initialize vcpkg
-      uses: actions/checkout@v3
+      uses: actions/checkout@v4
       with:
         repository: 'microsoft/vcpkg'
         path: 'compat/vcbuild/vcpkg'
@@ -212,7 +212,7 @@
     - name: zip up tracked files
       run: git archive -o artifacts/tracked.tar.gz HEAD
     - name: upload tracked files and build artifacts
-      uses: actions/upload-artifact@v3
+      uses: actions/upload-artifact@v4
       with:
         name: vs-artifacts
         path: artifacts
@@ -230,7 +230,7 @@
     steps:
     - uses: git-for-windows/setup-git-for-windows-sdk@v1
     - name: download tracked files and build artifacts
-      uses: actions/download-artifact@v3
+      uses: actions/download-artifact@v4
       with:
         name: vs-artifacts
         path: ${{github.workspace}}
@@ -248,7 +248,7 @@
       run: ci/print-test-failures.sh
     - name: Upload failed tests' directories
       if: failure() && env.FAILED_TEST_ARTIFACTS != ''
-      uses: actions/upload-artifact@v3
+      uses: actions/upload-artifact@v4
       with:
         name: failed-tests-windows
         path: ${{env.FAILED_TEST_ARTIFACTS}}
@@ -297,7 +297,7 @@
       runs_on_pool: ${{matrix.vector.pool}}
     runs-on: ${{matrix.vector.pool}}
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@v4
     - run: ci/install-dependencies.sh
     - run: ci/run-build-and-tests.sh
     - name: print test failures
@@ -305,10 +305,21 @@
       run: ci/print-test-failures.sh
     - name: Upload failed tests' directories
       if: failure() && env.FAILED_TEST_ARTIFACTS != ''
-      uses: actions/upload-artifact@v3
+      uses: actions/upload-artifact@v4
       with:
         name: failed-tests-${{matrix.vector.jobname}}
         path: ${{env.FAILED_TEST_ARTIFACTS}}
+  fuzz-smoke-test:
+    name: fuzz smoke test
+    needs: ci-config
+    if: needs.ci-config.outputs.enabled == 'yes'
+    env:
+      CC: clang
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v4
+    - run: ci/install-dependencies.sh
+    - run: ci/run-build-and-minimal-fuzzers.sh
   dockerized:
     name: ${{matrix.vector.jobname}} (${{matrix.vector.image}})
     needs: ci-config
@@ -331,9 +342,9 @@
     runs-on: ubuntu-latest
     container: ${{matrix.vector.image}}
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@v4
       if: matrix.vector.jobname != 'linux32'
-    - uses: actions/checkout@v1
+    - uses: actions/checkout@v1 # cannot be upgraded because Node.js Actions aren't supported in this container
       if: matrix.vector.jobname == 'linux32'
     - run: ci/install-docker-dependencies.sh
     - run: ci/run-build-and-tests.sh
@@ -342,13 +353,13 @@
       run: ci/print-test-failures.sh
     - name: Upload failed tests' directories
       if: failure() && env.FAILED_TEST_ARTIFACTS != '' && matrix.vector.jobname != 'linux32'
-      uses: actions/upload-artifact@v3
+      uses: actions/upload-artifact@v4
       with:
         name: failed-tests-${{matrix.vector.jobname}}
         path: ${{env.FAILED_TEST_ARTIFACTS}}
     - name: Upload failed tests' directories
       if: failure() && env.FAILED_TEST_ARTIFACTS != '' && matrix.vector.jobname == 'linux32'
-      uses: actions/upload-artifact@v1
+      uses: actions/upload-artifact@v1 # cannot be upgraded because Node.js Actions aren't supported in this container
       with:
         name: failed-tests-${{matrix.vector.jobname}}
         path: ${{env.FAILED_TEST_ARTIFACTS}}
@@ -362,7 +373,7 @@
       group: static-analysis-${{ github.ref }}
       cancel-in-progress: ${{ needs.ci-config.outputs.skip_concurrent == 'yes' }}
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@v4
     - run: ci/install-dependencies.sh
     - run: ci/run-static-analysis.sh
     - run: ci/check-directional-formatting.bash
@@ -385,7 +396,7 @@
         artifact: sparse-20.04
     - name: Install the current `sparse` package
       run: sudo dpkg -i sparse-20.04/sparse_*.deb
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@v4
     - name: Install other dependencies
       run: ci/install-dependencies.sh
     - run: make sparse
@@ -400,6 +411,6 @@
       jobname: Documentation
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@v4
     - run: ci/install-dependencies.sh
     - run: ci/test-documentation.sh
diff --git a/.gitignore b/.gitignore
index 5e56e47..612c0f6 100644
--- a/.gitignore
+++ b/.gitignore
@@ -135,6 +135,7 @@
 /git-remote-ext
 /git-repack
 /git-replace
+/git-replay
 /git-request-pull
 /git-rerere
 /git-reset
diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index cd98bcb..43bfbd8 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -7,7 +7,7 @@
     - if: $CI_COMMIT_TAG
     - if: $CI_COMMIT_REF_PROTECTED == "true"
 
-test:
+test:linux:
   image: $image
   before_script:
     - ./ci/install-docker-dependencies.sh
@@ -51,3 +51,45 @@
     paths:
       - t/failed-test-artifacts
     when: on_failure
+
+test:osx:
+  image: $image
+  tags:
+    - saas-macos-medium-m1
+  variables:
+    TEST_OUTPUT_DIRECTORY: "/Volumes/RAMDisk"
+  before_script:
+    # Create a 4GB RAM disk that we use to store test output on. This small hack
+    # significantly speeds up tests by more than a factor of 2 because the
+    # macOS runners use network-attached storage as disks, which is _really_
+    # slow with the many small writes that our tests do.
+    - sudo diskutil apfs create $(hdiutil attach -nomount ram://8192000) RAMDisk
+    - ./ci/install-dependencies.sh
+  script:
+    - ./ci/run-build-and-tests.sh
+  after_script:
+    - |
+      if test "$CI_JOB_STATUS" != 'success'
+      then
+        ./ci/print-test-failures.sh
+        mv "$TEST_OUTPUT_DIRECTORY"/failed-test-artifacts t/
+      fi
+  parallel:
+    matrix:
+      - jobname: osx-clang
+        image: macos-13-xcode-14
+        CC: clang
+  artifacts:
+    paths:
+      - t/failed-test-artifacts
+    when: on_failure
+
+static-analysis:
+  image: ubuntu:22.04
+  variables:
+    jobname: StaticAnalysis
+  before_script:
+    - ./ci/install-docker-dependencies.sh
+  script:
+    - ./ci/run-static-analysis.sh
+    - ./ci/check-directional-formatting.bash
diff --git a/Documentation/Makefile b/Documentation/Makefile
index b629176..3f2383a 100644
--- a/Documentation/Makefile
+++ b/Documentation/Makefile
@@ -122,6 +122,7 @@
 TECH_DOCS += technical/send-pack-pipeline
 TECH_DOCS += technical/shallow
 TECH_DOCS += technical/trivial-merge
+TECH_DOCS += technical/unit-tests
 SP_ARTICLES += $(TECH_DOCS)
 SP_ARTICLES += technical/api-index
 
diff --git a/Documentation/RelNotes/2.44.0.txt b/Documentation/RelNotes/2.44.0.txt
new file mode 100644
index 0000000..30dbdcf
--- /dev/null
+++ b/Documentation/RelNotes/2.44.0.txt
@@ -0,0 +1,314 @@
+Git v2.44 Release Notes
+=======================
+
+Backward Compatibility Notes
+
+ * "git chekcout -B <branch>" used to allow switching to a branch that
+   is in use on another worktree, but this was by mistake.  The users
+   need to use "--ignore-other-worktrees" option.
+
+
+UI, Workflows & Features
+
+ * "git add" and "git stash" learned to support the ":(attr:...)"
+   magic pathspec.
+
+ * "git rebase --autosquash" is now enabled for non-interactive rebase,
+   but it is still incompatible with the apply backend.
+
+ * Introduce "git replay", a tool meant on the server side without
+   working tree to recreate a history.
+
+ * "git merge-file" learned to take the "--diff-algorithm" option to
+   use algorithm different from the default "myers" diff.
+
+ * Command line completion (in contrib/) learned to complete path
+   arguments to the "add/set" subcommands of "git sparse-checkout"
+   better.
+
+ * "git checkout -B <branch> [<start-point>]" allowed a branch that is
+   in use in another worktree to be updated and checked out, which
+   might be a bit unexpected.  The rule has been tightened, which is a
+   breaking change.  "--ignore-other-worktrees" option is required to
+   unbreak you, if you are used to the current behaviour that "-B"
+   overrides the safety.
+
+ * The builtin_objectmode attribute is populated for each path
+   without adding anything in .gitattributes files, which would be
+   useful in magic pathspec, e.g., ":(attr:builtin_objectmode=100755)"
+   to limit to executables.
+
+ * "git fetch" learned to pay attention to "fetch.all" configuration
+   variable, which pretends as if "--all" was passed from the command
+   line when no remote parameter was given.
+
+ * In addition to (rather cryptic) Security Identifiers, show username
+   and domain in the error message when we barf on mismatch between
+   the Git directory and the current user on Windows.
+
+ * The error message given when "git branch -d branch" fails due to
+   commits unique to the branch has been split into an error and a new
+   conditional advice message.
+
+ * When given an existing but unreadable file as a configuration file,
+   gitweb behaved as if the file did not exist at all, but now it
+   errors out.  This is a change that may break backward compatibility.
+
+ * When $HOME/.gitignore is missing but XDG config file available, we
+   should write into the latter, not former.  "git gc" and "git
+   maintenance" wrote into a wrong "global config" file, which have
+   been corrected.
+
+ * Define "special ref" as a very narrow set that consists of
+   FETCH_HEAD and MERGE_HEAD, and clarify everything else that used to
+   be classified as such are actually just pseudorefs.
+
+ * All conditional "advice" messages show how to turn them off, which
+   becomes repetitive.  Setting advice.* configuration explicitly on
+   now omits the instruction part.
+
+ * The "disable repository discovery of a bare repository" check,
+   triggered by setting safe.bareRepository configuration variable to
+   'explicit', has been loosened to exclude the ".git/" directory inside
+   a non-bare repository from the check.  So you can do "cd .git &&
+   git cmd" to run a Git command that works on a bare repository without
+   explicitly specifying $GIT_DIR now.
+
+ * The completion script (in contrib/) learned more options that can
+   be used with "git log".
+
+ * The labels on conflict markers for the common ancestor, our version,
+   and the other version are available to custom 3-way merge driver
+   via %S, %X, and %Y placeholders.
+
+ * The write codepath for the reftable data learned to honor
+   core.fsync configuration.
+
+ * The "--fsck-objects" option of "git index-pack" now can take the
+   optional parameter to tweak severity of different fsck errors.
+
+ * The wincred credential backend has been taught to support oauth
+   refresh token the same way as credential-cache and
+   credential-libsecret backends.
+
+ * Command line completion support (in contrib/) has been
+   updated for "git bisect".
+
+ * "git branch" and friends learned to use the formatted text as
+   sorting key, not the underlying timestamp value, when the --sort
+   option is used with author or committer timestamp with a format
+   specifier (e.g., "--sort=creatordate:format:%H:%M:%S").
+
+
+Performance, Internal Implementation, Development Support etc.
+
+ * Process to add some form of low-level unit tests has started.
+
+ * Add support for GitLab CI.
+
+ * "git for-each-ref --no-sort" still sorted the refs alphabetically
+   which paid non-trivial cost.  It has been redefined to show output
+   in an unspecified order, to allow certain optimizations to take
+   advantage of.
+
+ * Simplify API implementation to delete references by eliminating
+   duplication.
+
+ * Subject approxidate() and show_date() machinery to OSS-Fuzz.
+
+ * A new helper to let us pretend that we called lstat() when we know
+   our cache_entry is up-to-date via fsmonitor.
+
+ * The optimization based on fsmonitor in the "diff --cached"
+   codepath is resurrected with the "fake-lstat" introduced earlier.
+
+ * Test balloon to use C99 "bool" type from <stdbool.h> has been
+   added.
+
+ * "git clone" has been prepared to allow cloning a repository with
+   non-default hash function into a repository that uses the reftable
+   backend.
+
+ * Streaming spans of packfile data used to be done only from a
+   single, primary, pack in a repository with multiple packfiles.  It
+   has been extended to allow reuse from other packfiles, too.
+
+ * Comment updates to help developers not to attempt to modify
+   messages from plumbing commands that must stay constant.
+
+   It might make sense to reassess the plumbing needs every few years,
+   but that should be done as a separate effort.
+
+ * Move test-ctype helper to the unit-test framework.
+
+ * Instead of manually creating refs/ hierarchy on disk upon a
+   creation of a secondary worktree, which is only usable via the
+   files backend, use the refs API to populate it.
+
+ * CI for GitLab learned to drive macOS jobs.
+
+ * A few tests to "git commit -o <pathspec>" and "git commit -i
+   <pathspec>" has been added.
+
+ * Tests on ref API are moved around to prepare for reftable.
+
+ * The Makefile often had to say "-L$(path) -R$(path)" that repeats
+   the path to the same library directory for link time and runtime.
+   A Makefile template is used to reduce such repetition.
+
+ * The priority queue test has been migrated to the unit testing
+   framework.
+
+ * Setting `feature.experimental` opts the user into multi-pack reuse
+   experiment
+
+ * Squelch node.js 16 deprecation warnings from GitHub Actions CI
+   by updating actions/github-script and actions/checkout that use
+   node.js 20.
+
+ * The mechanism to report the filename in the source code, used by
+   the unit-test machinery, assumed that the compiler expanded __FILE__
+   to the path to the source given to the $(CC), but some compilers
+   give full path, breaking the output.  This has been corrected.
+
+
+Fixes since v2.43
+-----------------
+
+ * The way CI testing used "prove" could lead to running the test
+   suite twice needlessly, which has been corrected.
+
+ * Update ref-related tests.
+
+ * "git format-patch --encode-email-headers" ignored the option when
+   preparing the cover letter, which has been corrected.
+
+ * Newer versions of Getopt::Long started giving warnings against our
+   (ab)use of it in "git send-email".  Bump the minimum version
+   requirement for Perl to 5.8.1 (from September 2002) to allow
+   simplifying our implementation.
+
+ * Earlier we stopped relying on commit-graph that (still) records
+   information about commits that are lost from the object store,
+   which has negative performance implications.  The default has been
+   flipped to disable this pessimization.
+
+ * Stale URLs have been updated to their current counterparts (or
+   archive.org) and HTTP links are replaced with working HTTPS links.
+
+ * trace2 streams used to record the URLs that potentially embed
+   authentication material, which has been corrected.
+
+ * The sample pre-commit hook that tries to catch introduction of new
+   paths that use potentially non-portable characters did not notice
+   an existing path getting renamed to such a problematic path, when
+   rename detection was enabled.
+
+ * The command line parser for the "log" family of commands was too
+   loose when parsing certain numbers, e.g., silently ignoring the
+   extra 'q' in "git log -n 1q" without complaining, which has been
+   tightened up.
+
+ * "git $cmd --end-of-options --rev -- --path" for some $cmd failed
+   to interpret "--rev" as a rev, and "--path" as a path.  This was
+   fixed for many programs like "reset" and "checkout".
+
+ * "git bisect reset" has been taught to clean up state files and refs
+   even when BISECT_START file is gone.
+
+ * Some codepaths did not correctly parse configuration variables
+   specified with valueless "true", which has been corrected.
+
+ * Code clean-up for sanity checking of command line options for "git
+   show-ref".
+
+ * The code to parse the From e-mail header has been updated to avoid
+   recursion.
+
+ * "git fetch --atomic" issued an unnecessary empty error message,
+   which has been corrected.
+
+ * Command line completion script (in contrib/) learned to work better
+   with the reftable backend.
+
+ * "git status" is taught to show both the branch being bisected and
+   being rebased when both are in effect at the same time.
+
+ * "git archive --list extra garbage" silently ignored excess command
+   line parameters, which has been corrected.
+
+ * "git sparse-checkout set" added default patterns even when the
+   patterns are being fed from the standard input, which has been
+   corrected.
+
+ * "git sparse-checkout (add|set) --[no-]cone --end-of-options" did
+   not handle "--end-of-options" correctly after a recent update.
+
+ * Unlike other environment variables that took the usual
+   true/false/yes/no as well as 0/1, GIT_FLUSH only understood 0/1,
+   which has been corrected.
+
+ * Clearing in-core repository (happens during e.g., "git fetch
+   --recurse-submodules" with commit graph enabled) made in-core
+   commit object in an inconsistent state by discarding the necessary
+   data from commit-graph too early, which has been corrected.
+
+ * Update to a new feature recently added, "git show-ref --exists".
+
+ * oss-fuzz tests are built and run in CI.
+   (merge c4a9cf1df3 js/oss-fuzz-build-in-ci later to maint).
+
+ * Rename detection logic ignored the final line of a file if it is an
+   incomplete line.
+
+ * GitHub CI update.
+   (merge 0188b2c8e0 pb/ci-github-skip-logs-for-broken-tests later to maint).
+
+ * "git diff --no-rename A B" did not disable rename detection but did
+   not trigger an error from the command line parser.
+
+ * "git archive --remote=<remote>" learned to talk over the smart
+   http (aka stateless) transport.
+   (merge 176cd68634 jx/remote-archive-over-smart-http later to maint).
+
+ * Fetching via protocol v0 over Smart HTTP transport sometimes failed
+   to correctly auto-follow tags.
+   (merge fba732c462 jk/fetch-auto-tag-following-fix later to maint).
+
+ * The documentation for the --exclude-per-directory option marked it
+   as deprecated, which confused readers into thinking there may be a
+   plan to remove it in the future, which was not our intention.
+   (merge 0009542cab jc/ls-files-doc-update later to maint).
+
+ * "git diff --no-index file1 file2" segfaulted while invoking the
+   external diff driver, which has been corrected.
+
+ * Rewrite //-comments to /* comments */ in files whose comments
+   prevalently use the latter.
+
+ * Cirrus CI jobs started breaking because we specified version of
+   FreeBSD that is no longer available, which has been corrected.
+   (merge 81fffb66d3 cb/use-freebsd-13-2-at-cirrus-ci later to maint).
+
+ * A caller called index_file_exists() that takes a string expressed
+   as <ptr, length> with a wrong length, which has been corrected.
+   (merge 156e28b36d jh/sparse-index-expand-to-path-fix later to maint).
+
+ * A failed "git tag -s" did not necessarily result in an error
+   depending on the crypto backend, which has been corrected.
+
+ * "git stash" sometimes was silent even when it failed due to
+   unwritable index file, which has been corrected.
+
+ * "git show-ref --verify" did not show things like "CHERRY_PICK_HEAD",
+   which has been corrected.
+
+ * Recent conversion to allow more than 0/1 in GIT_FLUSH broke the
+   mechanism by flipping what yes/no means by mistake, which has been
+   corrected.
+
+ * Other code cleanup, docfix, build fix, etc.
+   (merge 5aea3955bc rj/clarify-branch-doc-m later to maint).
+   (merge 9cce3be2df bk/bisect-doc-fix later to maint).
+   (merge 8430b438f6 vd/fsck-submodule-url-test later to maint).
+   (merge 3cb4384683 jc/t0091-with-unknown-git later to maint).
diff --git a/Documentation/config/advice.txt b/Documentation/config/advice.txt
index 4d7e5d8..c7ea70f 100644
--- a/Documentation/config/advice.txt
+++ b/Documentation/config/advice.txt
@@ -1,30 +1,63 @@
 advice.*::
 	These variables control various optional help messages designed to
-	aid new users. All 'advice.*' variables default to 'true', and you
-	can tell Git that you do not need help by setting these to 'false':
+	aid new users.  When left unconfigured, Git will give the message
+	alongside instructions on how to squelch it.  You can tell Git
+	that you do not need the help message by setting these to 'false':
 +
 --
+	addEmbeddedRepo::
+		Advice on what to do when you've accidentally added one
+		git repo inside of another.
+	addEmptyPathspec::
+		Advice shown if a user runs the add command without providing
+		the pathspec parameter.
+	addIgnoredFile::
+		Advice shown if a user attempts to add an ignored file to
+		the index.
+	amWorkDir::
+		Advice that shows the location of the patch file when
+		linkgit:git-am[1] fails to apply it.
 	ambiguousFetchRefspec::
 		Advice shown when a fetch refspec for multiple remotes maps to
 		the same remote-tracking branch namespace and causes branch
 		tracking set-up to fail.
+	checkoutAmbiguousRemoteBranchName::
+		Advice shown when the argument to
+		linkgit:git-checkout[1] and linkgit:git-switch[1]
+		ambiguously resolves to a
+		remote tracking branch on more than one remote in
+		situations where an unambiguous argument would have
+		otherwise caused a remote-tracking branch to be
+		checked out. See the `checkout.defaultRemote`
+		configuration variable for how to set a given remote
+		to be used by default in some situations where this
+		advice would be printed.
+	commitBeforeMerge::
+		Advice shown when linkgit:git-merge[1] refuses to
+		merge to avoid overwriting local changes.
+	detachedHead::
+		Advice shown when you used
+		linkgit:git-switch[1] or linkgit:git-checkout[1]
+		to move to the detached HEAD state, to instruct how to
+		create a local branch after the fact.
+	diverging::
+		Advice shown when a fast-forward is not possible.
 	fetchShowForcedUpdates::
 		Advice shown when linkgit:git-fetch[1] takes a long time
 		to calculate forced updates after ref updates, or to warn
 		that the check is disabled.
-	pushUpdateRejected::
-		Set this variable to 'false' if you want to disable
-		'pushNonFFCurrent', 'pushNonFFMatching', 'pushAlreadyExists',
-		'pushFetchFirst', 'pushNeedsForce', and 'pushRefNeedsUpdate'
-		simultaneously.
-	pushNonFFCurrent::
-		Advice shown when linkgit:git-push[1] fails due to a
-		non-fast-forward update to the current branch.
-	pushNonFFMatching::
-		Advice shown when you ran linkgit:git-push[1] and pushed
-		'matching refs' explicitly (i.e. you used ':', or
-		specified a refspec that isn't your current branch) and
-		it resulted in a non-fast-forward error.
+	forceDeleteBranch::
+		Advice shown when a user tries to delete a not fully merged
+		branch without the force option set.
+	ignoredHook::
+		Advice shown if a hook is ignored because the hook is not
+		set as executable.
+	implicitIdentity::
+		Advice on how to set your identity configuration when
+		your information is guessed from the system username and
+		domain name.
+	nestedTag::
+		Advice shown if a user attempts to recursively tag a tag object.
 	pushAlreadyExists::
 		Shown when linkgit:git-push[1] rejects an update that
 		does not qualify for fast-forwarding (e.g., a tag.)
@@ -37,6 +70,18 @@
 		tries to overwrite a remote ref that points at an
 		object that is not a commit-ish, or make the remote
 		ref point at an object that is not a commit-ish.
+	pushNonFFCurrent::
+		Advice shown when linkgit:git-push[1] fails due to a
+		non-fast-forward update to the current branch.
+	pushNonFFMatching::
+		Advice shown when you ran linkgit:git-push[1] and pushed
+		'matching refs' explicitly (i.e. you used ':', or
+		specified a refspec that isn't your current branch) and
+		it resulted in a non-fast-forward error.
+	pushRefNeedsUpdate::
+		Shown when linkgit:git-push[1] rejects a forced update of
+		a branch when its remote-tracking ref has updates that we
+		do not have locally.
 	pushUnqualifiedRefname::
 		Shown when linkgit:git-push[1] gives up trying to
 		guess based on the source and destination refs what
@@ -44,10 +89,23 @@
 		we can still suggest that the user push to either
 		refs/heads/* or refs/tags/* based on the type of the
 		source object.
-	pushRefNeedsUpdate::
-		Shown when linkgit:git-push[1] rejects a forced update of
-		a branch when its remote-tracking ref has updates that we
-		do not have locally.
+	pushUpdateRejected::
+		Set this variable to 'false' if you want to disable
+		'pushNonFFCurrent', 'pushNonFFMatching', 'pushAlreadyExists',
+		'pushFetchFirst', 'pushNeedsForce', and 'pushRefNeedsUpdate'
+		simultaneously.
+	resetNoRefresh::
+		Advice to consider using the `--no-refresh` option to
+		linkgit:git-reset[1] when the command takes more than 2 seconds
+		to refresh the index after reset.
+	resolveConflict::
+		Advice shown by various commands when conflicts
+		prevent the operation from being performed.
+	rmHints::
+		In case of failure in the output of linkgit:git-rm[1],
+		show directions on how to proceed from the current state.
+	sequencerInUse::
+		Advice shown when a sequencer command is already in progress.
 	skippedCherryPicks::
 		Shown when linkgit:git-rebase[1] skips a commit that has already
 		been cherry-picked onto the upstream branch.
@@ -68,76 +126,22 @@
 		Advise to consider using the `-u` option to linkgit:git-status[1]
 		when the command takes more than 2 seconds to enumerate untracked
 		files.
-	commitBeforeMerge::
-		Advice shown when linkgit:git-merge[1] refuses to
-		merge to avoid overwriting local changes.
-	resetNoRefresh::
-		Advice to consider using the `--no-refresh` option to
-		linkgit:git-reset[1] when the command takes more than 2 seconds
-		to refresh the index after reset.
-	resolveConflict::
-		Advice shown by various commands when conflicts
-		prevent the operation from being performed.
-	sequencerInUse::
-		Advice shown when a sequencer command is already in progress.
-	implicitIdentity::
-		Advice on how to set your identity configuration when
-		your information is guessed from the system username and
-		domain name.
-	detachedHead::
-		Advice shown when you used
-		linkgit:git-switch[1] or linkgit:git-checkout[1]
-		to move to the detached HEAD state, to instruct how to
-		create a local branch after the fact.
-	suggestDetachingHead::
-		Advice shown when linkgit:git-switch[1] refuses to detach HEAD
-		without the explicit `--detach` option.
-	checkoutAmbiguousRemoteBranchName::
-		Advice shown when the argument to
-		linkgit:git-checkout[1] and linkgit:git-switch[1]
-		ambiguously resolves to a
-		remote tracking branch on more than one remote in
-		situations where an unambiguous argument would have
-		otherwise caused a remote-tracking branch to be
-		checked out. See the `checkout.defaultRemote`
-		configuration variable for how to set a given remote
-		to be used by default in some situations where this
-		advice would be printed.
-	amWorkDir::
-		Advice that shows the location of the patch file when
-		linkgit:git-am[1] fails to apply it.
-	rmHints::
-		In case of failure in the output of linkgit:git-rm[1],
-		show directions on how to proceed from the current state.
-	addEmbeddedRepo::
-		Advice on what to do when you've accidentally added one
-		git repo inside of another.
-	ignoredHook::
-		Advice shown if a hook is ignored because the hook is not
-		set as executable.
-	waitingForEditor::
-		Print a message to the terminal whenever Git is waiting for
-		editor input from the user.
-	nestedTag::
-		Advice shown if a user attempts to recursively tag a tag object.
 	submoduleAlternateErrorStrategyDie::
 		Advice shown when a submodule.alternateErrorStrategy option
 		configured to "die" causes a fatal error.
 	submodulesNotUpdated::
 		Advice shown when a user runs a submodule command that fails
 		because `git submodule update --init` was not run.
-	addIgnoredFile::
-		Advice shown if a user attempts to add an ignored file to
-		the index.
-	addEmptyPathspec::
-		Advice shown if a user runs the add command without providing
-		the pathspec parameter.
+	suggestDetachingHead::
+		Advice shown when linkgit:git-switch[1] refuses to detach HEAD
+		without the explicit `--detach` option.
 	updateSparsePath::
 		Advice shown when either linkgit:git-add[1] or linkgit:git-rm[1]
 		is asked to update index entries outside the current sparse
 		checkout.
-	diverging::
-		Advice shown when a fast-forward is not possible.
+	waitingForEditor::
+		Print a message to the terminal whenever Git is waiting for
+		editor input from the user.
 	worktreeAddOrphan::
 		Advice shown when a user tries to create a worktree from an
 		invalid reference, to instruct how to create a new unborn
diff --git a/Documentation/config/extensions.txt b/Documentation/config/extensions.txt
index bccaec7..66db0e1 100644
--- a/Documentation/config/extensions.txt
+++ b/Documentation/config/extensions.txt
@@ -7,6 +7,17 @@
 linkgit:git-clone[1].  Trying to change it after initialization will not
 work and will produce hard-to-diagnose issues.
 
+extensions.refStorage::
+	Specify the ref storage format to use. The acceptable values are:
++
+include::../ref-storage-format.txt[]
++
+It is an error to specify this key unless `core.repositoryFormatVersion` is 1.
++
+Note that this setting should only be set by linkgit:git-init[1] or
+linkgit:git-clone[1]. Trying to change it after initialization will not
+work and will produce hard-to-diagnose issues.
+
 extensions.worktreeConfig::
 	If enabled, then worktrees will load config settings from the
 	`$GIT_DIR/config.worktree` file in addition to the
diff --git a/Documentation/config/feature.txt b/Documentation/config/feature.txt
index bf9546f..f061b64 100644
--- a/Documentation/config/feature.txt
+++ b/Documentation/config/feature.txt
@@ -17,6 +17,9 @@
 +
 * `pack.useBitmapBoundaryTraversal=true` may improve bitmap traversal times by
 walking fewer objects.
++
+* `pack.allowPackReuse=multi` may improve the time it takes to create a pack by
+reusing objects from multiple packs instead of just one.
 
 feature.manyFiles::
 	Enable config options that optimize for repos with many files in the
diff --git a/Documentation/config/fetch.txt b/Documentation/config/fetch.txt
index aea5b97..d7dc461 100644
--- a/Documentation/config/fetch.txt
+++ b/Documentation/config/fetch.txt
@@ -50,6 +50,12 @@
 	refs. See also `remote.<name>.pruneTags` and the PRUNING
 	section of linkgit:git-fetch[1].
 
+fetch.all::
+	If true, fetch will attempt to update all available remotes.
+	This behavior can be overridden by passing `--no-all` or by
+	explicitly specifying one or more remote(s) to fetch from.
+	Defaults to false.
+
 fetch.output::
 	Control how ref update status is printed. Valid values are
 	`full` and `compact`. Default value is `full`. See the
diff --git a/Documentation/config/pack.txt b/Documentation/config/pack.txt
index f50df9d..9c63086 100644
--- a/Documentation/config/pack.txt
+++ b/Documentation/config/pack.txt
@@ -28,11 +28,17 @@
 to linkgit:git-repack[1].
 
 pack.allowPackReuse::
-	When true, and when reachability bitmaps are enabled,
-	pack-objects will try to send parts of the bitmapped packfile
-	verbatim. This can reduce memory and CPU usage to serve fetches,
-	but might result in sending a slightly larger pack. Defaults to
-	true.
+	When true or "single", and when reachability bitmaps are
+	enabled, pack-objects will try to send parts of the bitmapped
+	packfile verbatim. When "multi", and when a multi-pack
+	reachability bitmap is available, pack-objects will try to send
+	parts of all packs in the MIDX.
++
+	If only a single pack bitmap is available, and
+	`pack.allowPackReuse` is set to "multi", reuse parts of just the
+	bitmapped packfile. This can reduce memory and CPU usage to
+	serve fetches, but might result in sending a slightly larger
+	pack. Defaults to true.
 
 pack.island::
 	An extended regular expression configuring a set of delta
diff --git a/Documentation/config/rebase.txt b/Documentation/config/rebase.txt
index 7c57c5e..c6187ab 100644
--- a/Documentation/config/rebase.txt
+++ b/Documentation/config/rebase.txt
@@ -9,7 +9,9 @@
 	rebase. False by default.
 
 rebase.autoSquash::
-	If set to true enable `--autosquash` option by default.
+	If set to true, enable the `--autosquash` option of
+	linkgit:git-rebase[1] by default for interactive mode.
+	This can be overridden with the `--no-autosquash` option.
 
 rebase.autoStash::
 	When set to true, automatically create a temporary stash entry
diff --git a/Documentation/diff-options.txt b/Documentation/diff-options.txt
index 53ec3c9..aaaff0d 100644
--- a/Documentation/diff-options.txt
+++ b/Documentation/diff-options.txt
@@ -299,7 +299,7 @@
 	Synonym for --dirstat=cumulative
 
 --dirstat-by-file[=<param1,param2>...]::
-	Synonym for --dirstat=files,param1,param2...
+	Synonym for --dirstat=files,<param1>,<param2>...
 
 --summary::
 	Output a condensed summary of extended header information
diff --git a/Documentation/fetch-options.txt b/Documentation/fetch-options.txt
index a1d6633..54ebb44 100644
--- a/Documentation/fetch-options.txt
+++ b/Documentation/fetch-options.txt
@@ -1,5 +1,6 @@
---all::
-	Fetch all remotes.
+--[no-]all::
+	Fetch all remotes. This overrides the configuration variable
+	`fetch.all`.
 
 -a::
 --append::
diff --git a/Documentation/git-bisect.txt b/Documentation/git-bisect.txt
index a0e75a6..82f944d 100644
--- a/Documentation/git-bisect.txt
+++ b/Documentation/git-bisect.txt
@@ -17,7 +17,7 @@
 on the subcommand:
 
  git bisect start [--term-(bad|new)=<term-new> --term-(good|old)=<term-old>]
-		  [--no-checkout] [--first-parent] [<bad> [<good>...]] [--] [<paths>...]
+		  [--no-checkout] [--first-parent] [<bad> [<good>...]] [--] [<pathspec>...]
  git bisect (bad|new|<term-new>) [<rev>]
  git bisect (good|old|<term-old>) [<rev>...]
  git bisect terms [--term-(good|old) | --term-(bad|new)]
@@ -301,7 +301,7 @@
 
 You can further cut down the number of trials, if you know what part of
 the tree is involved in the problem you are tracking down, by specifying
-path parameters when issuing the `bisect start` command:
+pathspec parameters when issuing the `bisect start` command:
 
 ------------
 $ git bisect start -- arch/i386 include/asm-i386
diff --git a/Documentation/git-blame.txt b/Documentation/git-blame.txt
index 5720d04..b1d7fb5 100644
--- a/Documentation/git-blame.txt
+++ b/Documentation/git-blame.txt
@@ -210,7 +210,7 @@
 
 . Each blame entry always starts with a line of:
 
-	<40-byte hex sha1> <sourceline> <resultline> <num_lines>
+	<40-byte-hex-sha1> <sourceline> <resultline> <num-lines>
 +
 Line numbers count from 1.
 
diff --git a/Documentation/git-branch.txt b/Documentation/git-branch.txt
index 4395aa9..0b08442 100644
--- a/Documentation/git-branch.txt
+++ b/Documentation/git-branch.txt
@@ -312,7 +312,8 @@
 	option is omitted, the current HEAD will be used instead.
 
 <oldbranch>::
-	The name of an existing branch to rename.
+	The name of an existing branch.  If this option is omitted,
+	the name of the current branch will be used instead.
 
 <newbranch>::
 	The new name for an existing branch. The same restrictions as for
diff --git a/Documentation/git-bugreport.txt b/Documentation/git-bugreport.txt
index 392d9eb..ca626f7 100644
--- a/Documentation/git-bugreport.txt
+++ b/Documentation/git-bugreport.txt
@@ -52,7 +52,7 @@
 -s <format>::
 --suffix <format>::
 	Specify an alternate suffix for the bugreport name, to create a file
-	named 'git-bugreport-<formatted suffix>'. This should take the form of a
+	named 'git-bugreport-<formatted-suffix>'. This should take the form of a
 	strftime(3) format string; the current local time will be used.
 
 --no-diagnose::
@@ -60,7 +60,7 @@
 	Create a zip archive of supplemental information about the user's
 	machine, Git client, and repository state. The archive is written to the
 	same output directory as the bug report and is named
-	'git-diagnostics-<formatted suffix>'.
+	'git-diagnostics-<formatted-suffix>'.
 +
 Without `mode` specified, the diagnostic archive will contain the default set of
 statistics reported by `git diagnose`. An optional `mode` value may be specified
diff --git a/Documentation/git-checkout.txt b/Documentation/git-checkout.txt
index 26ad1a5..8bdfa54 100644
--- a/Documentation/git-checkout.txt
+++ b/Documentation/git-checkout.txt
@@ -63,7 +63,9 @@
 ------------
 +
 that is to say, the branch is not reset/created unless "git checkout" is
-successful.
+successful (e.g., when the branch is in use in another worktree, not
+just the current branch stays the same, but the branch is not reset to
+the start-point, either).
 
 'git checkout' --detach [<branch>]::
 'git checkout' [--detach] <commit>::
diff --git a/Documentation/git-clone.txt b/Documentation/git-clone.txt
index c37c4a3..6e43eb9 100644
--- a/Documentation/git-clone.txt
+++ b/Documentation/git-clone.txt
@@ -311,6 +311,12 @@
 	The result is Git repository can be separated from working
 	tree.
 
+--ref-format=<ref-format::
+
+Specify the given ref storage format for the repository. The valid values are:
++
+include::ref-storage-format.txt[]
+
 -j <n>::
 --jobs <n>::
 	The number of submodules fetched at the same time.
diff --git a/Documentation/git-commit-graph.txt b/Documentation/git-commit-graph.txt
index c8dbceb..903b168 100644
--- a/Documentation/git-commit-graph.txt
+++ b/Documentation/git-commit-graph.txt
@@ -13,7 +13,7 @@
 'git commit-graph write' [--object-dir <dir>] [--append]
 			[--split[=<strategy>]] [--reachable | --stdin-packs | --stdin-commits]
 			[--changed-paths] [--[no-]max-new-filters <n>] [--[no-]progress]
-			<split options>
+			<split-options>
 
 
 DESCRIPTION
diff --git a/Documentation/git-config.txt b/Documentation/git-config.txt
index b1caac8..dff3909 100644
--- a/Documentation/git-config.txt
+++ b/Documentation/git-config.txt
@@ -103,11 +103,11 @@
 	names are not.
 
 --get-urlmatch <name> <URL>::
-	When given a two-part name section.key, the value for
-	section.<URL>.key whose <URL> part matches the best to the
+	When given a two-part <name> as <section>.<key>, the value for
+	<section>.<URL>.<key> whose <URL> part matches the best to the
 	given URL is returned (if no such key exists, the value for
-	section.key is used as a fallback).  When given just the
-	section as name, do so for all the keys in the section and
+	<section>.<key> is used as a fallback).  When given just the
+	<section> as name, do so for all the keys in the section and
 	list them.  Returns error code 1 if no value is found.
 
 --global::
diff --git a/Documentation/git-cvsserver.txt b/Documentation/git-cvsserver.txt
index cf4a5a2..4c475ef 100644
--- a/Documentation/git-cvsserver.txt
+++ b/Documentation/git-cvsserver.txt
@@ -197,7 +197,7 @@
 5. Clients should now be able to check out the project. Use the CVS 'module'
    name to indicate what Git 'head' you want to check out.  This also sets the
    name of your newly checked-out directory, unless you tell it otherwise with
-   `-d <dir_name>`.  For example, this checks out 'master' branch to the
+   `-d <dir-name>`.  For example, this checks out 'master' branch to the
    `project-master` directory:
 +
 ------
@@ -224,7 +224,7 @@
 that the database is up to date any time 'git-cvsserver' is executed).
 
 By default it uses SQLite databases in the Git directory, named
-`gitcvs.<module_name>.sqlite`. Note that the SQLite backend creates
+`gitcvs.<module-name>.sqlite`. Note that the SQLite backend creates
 temporary files in the same directory as the database file on
 write so it might not be enough to grant the users using
 'git-cvsserver' write access to the database file without granting
diff --git a/Documentation/git-daemon.txt b/Documentation/git-daemon.txt
index e064f91..ede7b93 100644
--- a/Documentation/git-daemon.txt
+++ b/Documentation/git-daemon.txt
@@ -18,7 +18,7 @@
 	     [--allow-override=<service>] [--forbid-override=<service>]
 	     [--access-hook=<path>] [--[no-]informative-errors]
 	     [--inetd |
-	      [--listen=<host_or_ipaddr>] [--port=<n>]
+	      [--listen=<host-or-ipaddr>] [--port=<n>]
 	      [--user=<user> [--group=<group>]]]
 	     [--log-destination=(stderr|syslog|none)]
 	     [<directory>...]
@@ -86,10 +86,10 @@
 	Incompatible with --detach, --port, --listen, --user and --group
 	options.
 
---listen=<host_or_ipaddr>::
+--listen=<host-or-ipaddr>::
 	Listen on a specific IP address or hostname.  IP addresses can
 	be either an IPv4 address or an IPv6 address if supported.  If IPv6
-	is not supported, then --listen=hostname is also not supported and
+	is not supported, then --listen=<hostname> is also not supported and
 	--listen must be given an IPv4 address.
 	Can be given more than once.
 	Incompatible with `--inetd` option.
@@ -141,8 +141,8 @@
 	specified with no parameter, a request to
 	git://host/{tilde}alice/foo is taken as a request to access
 	'foo' repository in the home directory of user `alice`.
-	If `--user-path=path` is specified, the same request is
-	taken as a request to access `path/foo` repository in
+	If `--user-path=<path>` is specified, the same request is
+	taken as a request to access `<path>/foo` repository in
 	the home directory of user `alice`.
 
 --verbose::
diff --git a/Documentation/git-diagnose.txt b/Documentation/git-diagnose.txt
index 3ec8cc7..0711959 100644
--- a/Documentation/git-diagnose.txt
+++ b/Documentation/git-diagnose.txt
@@ -45,7 +45,7 @@
 -s <format>::
 --suffix <format>::
 	Specify an alternate suffix for the diagnostics archive name, to create
-	a file named 'git-diagnostics-<formatted suffix>'. This should take the
+	a file named 'git-diagnostics-<formatted-suffix>'. This should take the
 	form of a strftime(3) format string; the current local time will be
 	used.
 
diff --git a/Documentation/git-difftool.txt b/Documentation/git-difftool.txt
index 50cb080..c05f97a 100644
--- a/Documentation/git-difftool.txt
+++ b/Documentation/git-difftool.txt
@@ -90,7 +90,7 @@
 --extcmd=<command>::
 	Specify a custom command for viewing diffs.
 	'git-difftool' ignores the configured defaults and runs
-	`$command $LOCAL $REMOTE` when this option is specified.
+	`<command> $LOCAL $REMOTE` when this option is specified.
 	Additionally, `$BASE` is set in the environment.
 
 -g::
diff --git a/Documentation/git-fast-import.txt b/Documentation/git-fast-import.txt
index bd7b1e0..b260736 100644
--- a/Documentation/git-fast-import.txt
+++ b/Documentation/git-fast-import.txt
@@ -745,11 +745,11 @@
 
 `notemodify`
 ^^^^^^^^^^^^
-Included in a `commit` `<notes_ref>` command to add a new note
+Included in a `commit` `<notes-ref>` command to add a new note
 annotating a `<commit-ish>` or change this annotation contents.
 Internally it is similar to filemodify 100644 on `<commit-ish>`
 path (maybe split into subdirectories). It's not advised to
-use any other commands to write to the `<notes_ref>` tree except
+use any other commands to write to the `<notes-ref>` tree except
 `filedeleteall` to delete all existing notes in this tree.
 This command has two different means of specifying the content
 of the note.
diff --git a/Documentation/git-fetch.txt b/Documentation/git-fetch.txt
index f123139..50900a5 100644
--- a/Documentation/git-fetch.txt
+++ b/Documentation/git-fetch.txt
@@ -186,8 +186,8 @@
 ------------------------------------------------
 $ git fetch origin --prune --prune-tags
 $ git fetch origin --prune 'refs/tags/*:refs/tags/*'
-$ git fetch <url of origin> --prune --prune-tags
-$ git fetch <url of origin> --prune 'refs/tags/*:refs/tags/*'
+$ git fetch <url-of-origin> --prune --prune-tags
+$ git fetch <url-of-origin> --prune 'refs/tags/*:refs/tags/*'
 ------------------------------------------------
 
 OUTPUT
diff --git a/Documentation/git-filter-branch.txt b/Documentation/git-filter-branch.txt
index 62e482a..5a4f853 100644
--- a/Documentation/git-filter-branch.txt
+++ b/Documentation/git-filter-branch.txt
@@ -14,7 +14,7 @@
 	[--msg-filter <command>] [--commit-filter <command>]
 	[--tag-name-filter <command>] [--prune-empty]
 	[--original <namespace>] [-d <directory>] [-f | --force]
-	[--state-branch <branch>] [--] [<rev-list options>...]
+	[--state-branch <branch>] [--] [<rev-list-options>...]
 
 WARNING
 -------
@@ -32,7 +32,7 @@
 DESCRIPTION
 -----------
 Lets you rewrite Git revision history by rewriting the branches mentioned
-in the <rev-list options>, applying custom filters on each revision.
+in the <rev-list-options>, applying custom filters on each revision.
 Those filters can modify each tree (e.g. removing a file or running
 a perl rewrite on all files) or information about each commit.
 Otherwise, all information (including original commit times or merge
@@ -624,7 +624,7 @@
      real backup; it dereferences tags first.)
 
   ** Running git-filter-branch with either --tags or --all in your
-     <rev-list options>.  In order to retain annotated tags as
+     <rev-list-options>.  In order to retain annotated tags as
      annotated, you must use --tag-name-filter (and must not have
      restored from refs/original/ in a previously botched rewrite).
 
diff --git a/Documentation/git-for-each-ref.txt b/Documentation/git-for-each-ref.txt
index e86d570..3a9ad91 100644
--- a/Documentation/git-for-each-ref.txt
+++ b/Documentation/git-for-each-ref.txt
@@ -51,17 +51,14 @@
 	key.
 
 --format=<format>::
-	A string that interpolates `%(fieldname)` from a ref being shown
-	and the object it points at.  If `fieldname`
-	is prefixed with an asterisk (`*`) and the ref points
-	at a tag object, use the value for the field in the object
-	which the tag object refers to (instead of the field in the tag object).
-	When unspecified, `<format>` defaults to
-	`%(objectname) SPC %(objecttype) TAB %(refname)`.
-	It also interpolates `%%` to `%`, and `%xx` where `xx`
-	are hex digits interpolates to character with hex code
-	`xx`; for example `%00` interpolates to `\0` (NUL),
-	`%09` to `\t` (TAB) and `%0a` to `\n` (LF).
+	A string that interpolates `%(fieldname)` from a ref being shown and
+	the object it points at. In addition, the string literal `%%`
+	renders as `%` and `%xx` - where `xx` are hex digits - renders as
+	the character with hex code `xx`. For example, `%00` interpolates to
+	`\0` (NUL), `%09` to `\t` (TAB), and `%0a` to `\n` (LF).
++
+When unspecified, `<format>` defaults to `%(objectname) SPC %(objecttype)
+TAB %(refname)`.
 
 --color[=<when>]::
 	Respect any colors specified in the `--format` option. The
@@ -298,6 +295,10 @@
 from the `committer` or `tagger` fields depending on the object type.
 These are intended for working on a mix of annotated and lightweight tags.
 
+For tag objects, a `fieldname` prefixed with an asterisk (`*`) expands to
+the `fieldname` value of the peeled object, rather than that of the tag
+object itself.
+
 Fields that have name-email-date tuple as its value (`author`,
 `committer`, and `tagger`) can be suffixed with `name`, `email`,
 and `date` to extract the named component.  For email fields (`authoremail`,
@@ -358,9 +359,11 @@
 the object referred by the ref does not cause an error.  It
 returns an empty string instead.
 
-As a special case for the date-type fields, you may specify a format for
-the date by adding `:` followed by date format name (see the
-values the `--date` option to linkgit:git-rev-list[1] takes).
+As a special case for the date-type fields, you may specify a format for the
+date by adding `:` followed by date format name (see the values the `--date`
+option to linkgit:git-rev-list[1] takes). If this formatting is provided in
+a `--sort` key, references will be sorted according to the byte-value of the
+formatted string rather than the numeric value of the underlying timestamp.
 
 Some atoms like %(align) and %(if) always require a matching %(end).
 We call them "opening atoms" and sometimes denote them as %($open).
diff --git a/Documentation/git-format-patch.txt b/Documentation/git-format-patch.txt
index 414da6b..728bb38 100644
--- a/Documentation/git-format-patch.txt
+++ b/Documentation/git-format-patch.txt
@@ -17,10 +17,10 @@
 		   [--signature-file=<file>]
 		   [-n | --numbered | -N | --no-numbered]
 		   [--start-number <n>] [--numbered-files]
-		   [--in-reply-to=<message id>] [--suffix=.<sfx>]
+		   [--in-reply-to=<message-id>] [--suffix=.<sfx>]
 		   [--ignore-if-in-upstream] [--always]
 		   [--cover-from-description=<mode>]
-		   [--rfc] [--subject-prefix=<subject prefix>]
+		   [--rfc] [--subject-prefix=<subject-prefix>]
 		   [(--reroll-count|-v) <n>]
 		   [--to=<email>] [--cc=<email>]
 		   [--[no-]cover-letter] [--quiet]
@@ -30,8 +30,8 @@
 		   [--range-diff=<previous> [--creation-factor=<percent>]]
 		   [--filename-max-length=<n>]
 		   [--progress]
-		   [<common diff options>]
-		   [ <since> | <revision range> ]
+		   [<common-diff-options>]
+		   [ <since> | <revision-range> ]
 
 DESCRIPTION
 -----------
@@ -64,7 +64,7 @@
    to the tip of the current branch that are not in the history
    that leads to the <since> to be output.
 
-2. Generic <revision range> expression (see "SPECIFYING
+2. Generic <revision-range> expression (see "SPECIFYING
    REVISIONS" section in linkgit:gitrevisions[7]) means the
    commits in the specified range.
 
@@ -179,9 +179,9 @@
 itself.  If you want `git format-patch` to take care of threading, you
 will want to ensure that threading is disabled for `git send-email`.
 
---in-reply-to=<message id>::
+--in-reply-to=<message-id>::
 	Make the first mail (or all the mails with `--no-thread`) appear as a
-	reply to the given <message id>, which avoids breaking threads to
+	reply to the given <message-id>, which avoids breaking threads to
 	provide a new patch series.
 
 --ignore-if-in-upstream::
@@ -219,9 +219,9 @@
 	Use the contents of <file> instead of the branch's description
 	for generating the cover letter.
 
---subject-prefix=<subject prefix>::
+--subject-prefix=<subject-prefix>::
 	Instead of the standard '[PATCH]' prefix in the subject
-	line, instead use '[<subject prefix>]'. This can be used
+	line, instead use '[<subject-prefix>]'. This can be used
 	to name a patch series, and can be combined with the
 	`--numbered` option.
 +
@@ -403,7 +403,7 @@
 	`format.useAutoBase` configuration.
 
 --root::
-	Treat the revision argument as a <revision range>, even if it
+	Treat the revision argument as a <revision-range>, even if it
 	is just a single commit (that would normally be treated as a
 	<since>).  Note that root commits included in the specified
 	range are always formatted as creation patches, independently
diff --git a/Documentation/git-index-pack.txt b/Documentation/git-index-pack.txt
index 6486620..5a20dee 100644
--- a/Documentation/git-index-pack.txt
+++ b/Documentation/git-index-pack.txt
@@ -79,8 +79,13 @@
 	to force the version for the generated pack index, and to force
 	64-bit index entries on objects located above the given offset.
 
---strict::
-	Die, if the pack contains broken objects or links.
+--strict[=<msg-id>=<severity>...]::
+	Die, if the pack contains broken objects or links. An optional
+	comma-separated list of `<msg-id>=<severity>` can be passed to change
+	the severity of some possible issues, e.g.,
+	 `--strict="missingEmail=ignore,badTagName=error"`. See the entry for the
+	`fsck.<msg-id>` configuration options in linkgit:git-fsck[1] for more
+	information on the possible values of `<msg-id>` and `<severity>`.
 
 --progress-title::
 	For internal use only.
@@ -91,13 +96,18 @@
 --check-self-contained-and-connected::
 	Die if the pack contains broken links. For internal use only.
 
---fsck-objects::
-	For internal use only.
+--fsck-objects[=<msg-id>=<severity>...]::
+	Die if the pack contains broken objects, but unlike `--strict`, don't
+	choke on broken links. If the pack contains a tree pointing to a
+	.gitmodules blob that does not exist, prints the hash of that blob
+	(for the caller to check) after the hash that goes into the name of the
+	pack/idx file (see "Notes").
 +
-Die if the pack contains broken objects. If the pack contains a tree
-pointing to a .gitmodules blob that does not exist, prints the hash of
-that blob (for the caller to check) after the hash that goes into the
-name of the pack/idx file (see "Notes").
+An optional comma-separated list of `<msg-id>=<severity>` can be passed to
+change the severity of some possible issues, e.g.,
+`--fsck-objects="missingEmail=ignore,badTagName=ignore"`. See the entry for the
+`fsck.<msg-id>` configuration options in linkgit:git-fsck[1] for more
+information on the possible values of `<msg-id>` and `<severity>`.
 
 --threads=<n>::
 	Specifies the number of threads to spawn when resolving
diff --git a/Documentation/git-init.txt b/Documentation/git-init.txt
index 6f0d297..e8dc645 100644
--- a/Documentation/git-init.txt
+++ b/Documentation/git-init.txt
@@ -11,6 +11,7 @@
 [verse]
 'git init' [-q | --quiet] [--bare] [--template=<template-directory>]
 	  [--separate-git-dir <git-dir>] [--object-format=<format>]
+	  [--ref-format=<format>]
 	  [-b <branch-name> | --initial-branch=<branch-name>]
 	  [--shared[=<permissions>]] [<directory>]
 
@@ -57,6 +58,12 @@
 +
 include::object-format-disclaimer.txt[]
 
+--ref-format=<format>::
+
+Specify the given ref storage format for the repository. The valid values are:
++
+include::ref-storage-format.txt[]
+
 --template=<template-directory>::
 
 Specify the directory from which templates will be used.  (See the "TEMPLATE
diff --git a/Documentation/git-ls-files.txt b/Documentation/git-ls-files.txt
index f65a8cd..d08c7da 100644
--- a/Documentation/git-ls-files.txt
+++ b/Documentation/git-ls-files.txt
@@ -119,8 +119,10 @@
 
 --exclude-per-directory=<file>::
 	Read additional exclude patterns that apply only to the
-	directory and its subdirectories in <file>.  Deprecated; use
-	--exclude-standard instead.
+	directory and its subdirectories in <file>.  If you are
+	trying to emulate the way Porcelain commands work, using
+	the `--exclude-standard` option instead is easier and more
+	thorough.
 
 --exclude-standard::
 	Add the standard Git exclusions: .git/info/exclude, .gitignore
@@ -298,9 +300,8 @@
 flags --others or --ignored are specified.  linkgit:gitignore[5]
 specifies the format of exclude patterns.
 
-Generally, you should just use --exclude-standard, but for historical
-reasons the exclude patterns can be specified from the following
-places, in order:
+These exclude patterns can be specified from the following places,
+in order:
 
   1. The command-line flag --exclude=<pattern> specifies a
      single pattern.  Patterns are ordered in the same order
@@ -322,6 +323,18 @@
 by --exclude-per-directory is relative to the directory that the
 pattern file appears in.
 
+Generally, you should be able to use `--exclude-standard` when you
+want the exclude rules applied the same way as what Porcelain
+commands do.  To emulate what `--exclude-standard` specifies, you
+can give `--exclude-per-directory=.gitignore`, and then specify:
+
+  1. The file specified by the `core.excludesfile` configuration
+     variable, if exists, or the `$XDG_CONFIG_HOME/git/ignore` file.
+
+  2. The `$GIT_DIR/info/exclude` file.
+
+via the `--exclude-from=` option.
+
 SEE ALSO
 --------
 linkgit:git-read-tree[1], linkgit:gitignore[5]
diff --git a/Documentation/git-merge-file.txt b/Documentation/git-merge-file.txt
index 6a081ea..71915a0 100644
--- a/Documentation/git-merge-file.txt
+++ b/Documentation/git-merge-file.txt
@@ -92,6 +92,12 @@
 	Instead of leaving conflicts in the file, resolve conflicts
 	favouring our (or their or both) side of the lines.
 
+--diff-algorithm={patience|minimal|histogram|myers}::
+	Use a different diff algorithm while merging. The current default is "myers",
+	but selecting more recent algorithm such as "histogram" can help
+	avoid mismerges that occur due to unimportant matching lines
+	(such as braces from distinct functions). See also
+	linkgit:git-diff[1] `--diff-algorithm`.
 
 EXAMPLES
 --------
diff --git a/Documentation/git-mv.txt b/Documentation/git-mv.txt
index 7f991a3..dc1bf61 100644
--- a/Documentation/git-mv.txt
+++ b/Documentation/git-mv.txt
@@ -16,7 +16,7 @@
 Move or rename a file, directory, or symlink.
 
  git mv [-v] [-f] [-n] [-k] <source> <destination>
- git mv [-v] [-f] [-n] [-k] <source> ... <destination directory>
+ git mv [-v] [-f] [-n] [-k] <source> ... <destination-directory>
 
 In the first form, it renames <source>, which must exist and be either
 a file, symlink or directory, to <destination>.
diff --git a/Documentation/git-notes.txt b/Documentation/git-notes.txt
index f8310e5..c9221a6 100644
--- a/Documentation/git-notes.txt
+++ b/Documentation/git-notes.txt
@@ -56,7 +56,7 @@
 list::
 	List the notes object for a given object. If no object is
 	given, show a list of all note objects and the objects they
-	annotate (in the format "<note object> <annotated object>").
+	annotate (in the format "<note-object> <annotated-object>").
 	This is the default subcommand if no subcommand is given.
 
 add::
diff --git a/Documentation/git-rebase.txt b/Documentation/git-rebase.txt
index af05708..0620652 100644
--- a/Documentation/git-rebase.txt
+++ b/Documentation/git-rebase.txt
@@ -589,21 +589,27 @@
 
 --autosquash::
 --no-autosquash::
-	When the commit log message begins with "squash! ..." or "fixup! ..."
-	or "amend! ...", and there is already a commit in the todo list that
-	matches the same `...`, automatically modify the todo list of
-	`rebase -i`, so that the commit marked for squashing comes right after
-	the commit to be modified, and change the action of the moved commit
-	from `pick` to `squash` or `fixup` or `fixup -C` respectively. A commit
-	matches the `...` if the commit subject matches, or if the `...` refers
-	to the commit's hash. As a fall-back, partial matches of the commit
-	subject work, too. The recommended way to create fixup/amend/squash
-	commits is by using the `--fixup`, `--fixup=amend:` or `--fixup=reword:`
-	and `--squash` options respectively of linkgit:git-commit[1].
+	Automatically squash commits with specially formatted messages into
+	previous commits being rebased.  If a commit message starts with
+	"squash! ", "fixup! " or "amend! ", the remainder of the subject line
+	is taken as a commit specifier, which matches a previous commit if it
+	matches the subject line or the hash of that commit.  If no commit
+	matches fully, matches of the specifier with the start of commit
+	subjects are considered.
 +
-If the `--autosquash` option is enabled by default using the
-configuration variable `rebase.autoSquash`, this option can be
-used to override and disable this setting.
+In the rebase todo list, the actions of squash, fixup and amend commits are
+changed from `pick` to `squash`, `fixup` or `fixup -C`, respectively, and they
+are moved right after the commit they modify.  The `--interactive` option can
+be used to review and edit the todo list before proceeding.
++
+The recommended way to create commits with squash markers is by using the
+`--squash`, `--fixup`, `--fixup=amend:` or `--fixup=reword:` options of
+linkgit:git-commit[1], which take the target commit as an argument and
+automatically fill in the subject line of the new commit from that.
++
+Settting configuration variable `rebase.autoSquash` to true enables
+auto-squashing by default for interactive rebase.  The `--no-autosquash`
+option can be used to override that setting.
 +
 See also INCOMPATIBLE OPTIONS below.
 
diff --git a/Documentation/git-replace.txt b/Documentation/git-replace.txt
index 4f25712..0a65460 100644
--- a/Documentation/git-replace.txt
+++ b/Documentation/git-replace.txt
@@ -114,11 +114,11 @@
 The following formats are available:
 
 * 'short':
-	<replaced sha1>
+	<replaced-sha1>
 * 'medium':
-	<replaced sha1> -> <replacement sha1>
+	<replaced-sha1> -> <replacement-sha1>
 * 'long':
-	<replaced sha1> (<replaced type>) -> <replacement sha1> (<replacement type>)
+	<replaced-sha1> (<replaced-type>) -> <replacement-sha1> (<replacement-type>)
 
 CREATING REPLACEMENT OBJECTS
 ----------------------------
diff --git a/Documentation/git-replay.txt b/Documentation/git-replay.txt
new file mode 100644
index 0000000..f6c269c
--- /dev/null
+++ b/Documentation/git-replay.txt
@@ -0,0 +1,127 @@
+git-replay(1)
+=============
+
+NAME
+----
+git-replay - EXPERIMENTAL: Replay commits on a new base, works with bare repos too
+
+
+SYNOPSIS
+--------
+[verse]
+(EXPERIMENTAL!) 'git replay' ([--contained] --onto <newbase> | --advance <branch>) <revision-range>...
+
+DESCRIPTION
+-----------
+
+Takes ranges of commits and replays them onto a new location. Leaves
+the working tree and the index untouched, and updates no references.
+The output of this command is meant to be used as input to
+`git update-ref --stdin`, which would update the relevant branches
+(see the OUTPUT section below).
+
+THIS COMMAND IS EXPERIMENTAL. THE BEHAVIOR MAY CHANGE.
+
+OPTIONS
+-------
+
+--onto <newbase>::
+	Starting point at which to create the new commits.  May be any
+	valid commit, and not just an existing branch name.
++
+When `--onto` is specified, the update-ref command(s) in the output will
+update the branch(es) in the revision range to point at the new
+commits, similar to the way how `git rebase --update-refs` updates
+multiple branches in the affected range.
+
+--advance <branch>::
+	Starting point at which to create the new commits; must be a
+	branch name.
++
+When `--advance` is specified, the update-ref command(s) in the output
+will update the branch passed as an argument to `--advance` to point at
+the new commits (in other words, this mimics a cherry-pick operation).
+
+<revision-range>::
+	Range of commits to replay. More than one <revision-range> can
+	be passed, but in `--advance <branch>` mode, they should have
+	a single tip, so that it's clear where <branch> should point
+	to. See "Specifying Ranges" in linkgit:git-rev-parse and the
+	"Commit Limiting" options below.
+
+include::rev-list-options.txt[]
+
+OUTPUT
+------
+
+When there are no conflicts, the output of this command is usable as
+input to `git update-ref --stdin`.  It is of the form:
+
+	update refs/heads/branch1 ${NEW_branch1_HASH} ${OLD_branch1_HASH}
+	update refs/heads/branch2 ${NEW_branch2_HASH} ${OLD_branch2_HASH}
+	update refs/heads/branch3 ${NEW_branch3_HASH} ${OLD_branch3_HASH}
+
+where the number of refs updated depends on the arguments passed and
+the shape of the history being replayed.  When using `--advance`, the
+number of refs updated is always one, but for `--onto`, it can be one
+or more (rebasing multiple branches simultaneously is supported).
+
+EXIT STATUS
+-----------
+
+For a successful, non-conflicted replay, the exit status is 0.  When
+the replay has conflicts, the exit status is 1.  If the replay is not
+able to complete (or start) due to some kind of error, the exit status
+is something other than 0 or 1.
+
+EXAMPLES
+--------
+
+To simply rebase `mybranch` onto `target`:
+
+------------
+$ git replay --onto target origin/main..mybranch
+update refs/heads/mybranch ${NEW_mybranch_HASH} ${OLD_mybranch_HASH}
+------------
+
+To cherry-pick the commits from mybranch onto target:
+
+------------
+$ git replay --advance target origin/main..mybranch
+update refs/heads/target ${NEW_target_HASH} ${OLD_target_HASH}
+------------
+
+Note that the first two examples replay the exact same commits and on
+top of the exact same new base, they only differ in that the first
+provides instructions to make mybranch point at the new commits and
+the second provides instructions to make target point at them.
+
+What if you have a stack of branches, one depending upon another, and
+you'd really like to rebase the whole set?
+
+------------
+$ git replay --contained --onto origin/main origin/main..tipbranch
+update refs/heads/branch1 ${NEW_branch1_HASH} ${OLD_branch1_HASH}
+update refs/heads/branch2 ${NEW_branch2_HASH} ${OLD_branch2_HASH}
+update refs/heads/tipbranch ${NEW_tipbranch_HASH} ${OLD_tipbranch_HASH}
+------------
+
+When calling `git replay`, one does not need to specify a range of
+commits to replay using the syntax `A..B`; any range expression will
+do:
+
+------------
+$ git replay --onto origin/main ^base branch1 branch2 branch3
+update refs/heads/branch1 ${NEW_branch1_HASH} ${OLD_branch1_HASH}
+update refs/heads/branch2 ${NEW_branch2_HASH} ${OLD_branch2_HASH}
+update refs/heads/branch3 ${NEW_branch3_HASH} ${OLD_branch3_HASH}
+------------
+
+This will simultaneously rebase `branch1`, `branch2`, and `branch3`,
+all commits they have since `base`, playing them on top of
+`origin/main`. These three branches may have commits on top of `base`
+that they have in common, but that does not need to be the case.
+
+GIT
+---
+Part of the linkgit:git[1] suite
diff --git a/Documentation/git-rev-parse.txt b/Documentation/git-rev-parse.txt
index 912fab9..546faf9 100644
--- a/Documentation/git-rev-parse.txt
+++ b/Documentation/git-rev-parse.txt
@@ -307,6 +307,9 @@
 	input, multiple algorithms may be printed, space-separated.
 	If not specified, the default is "storage".
 
+--show-ref-format::
+	Show the reference storage format used for the repository.
+
 
 Other Options
 ~~~~~~~~~~~~~
diff --git a/Documentation/git-revert.txt b/Documentation/git-revert.txt
index cbe0208..568925d 100644
--- a/Documentation/git-revert.txt
+++ b/Documentation/git-revert.txt
@@ -116,7 +116,7 @@
 
 --reference::
 	Instead of starting the body of the log message with "This
-	reverts <full object name of the commit being reverted>.",
+	reverts <full-object-name-of-the-commit-being-reverted>.",
 	refer to the commit using "--pretty=reference" format
 	(cf. linkgit:git-log[1]).  The `revert.reference`
 	configuration variable can be used to enable this option by
@@ -149,7 +149,7 @@
 _strongly_ recommended to explain why the original commit is being
 reverted.
 In addition, repeatedly reverting reverts will result in increasingly
-unwieldy subject lines, for example 'Reapply "Reapply "<original subject>""'.
+unwieldy subject lines, for example 'Reapply "Reapply "<original-subject>""'.
 Please consider rewording these to be shorter and more unique.
 
 CONFIGURATION
diff --git a/Documentation/git-send-email.txt b/Documentation/git-send-email.txt
index 30deb7f..d1ef6a2 100644
--- a/Documentation/git-send-email.txt
+++ b/Documentation/git-send-email.txt
@@ -10,7 +10,7 @@
 --------
 [verse]
 'git send-email' [<options>] <file|directory>...
-'git send-email' [<options>] <format-patch options>
+'git send-email' [<options>] <format-patch-options>
 'git send-email' --dump-aliases
 
 
diff --git a/Documentation/git-status.txt b/Documentation/git-status.txt
index 10fecc5..4dbb883 100644
--- a/Documentation/git-status.txt
+++ b/Documentation/git-status.txt
@@ -309,7 +309,7 @@
 ------------------------------------------------------------
 # branch.oid <commit> | (initial)        Current commit.
 # branch.head <branch> | (detached)      Current branch.
-# branch.upstream <upstream_branch>      If upstream is set.
+# branch.upstream <upstream-branch>      If upstream is set.
 # branch.ab +<ahead> -<behind>           If upstream is set and
 					 the commit is present.
 ------------------------------------------------------------
@@ -502,7 +502,7 @@
 	usually worth the additional size.
 
 * `core.untrackedCache=true` and `core.fsmonitor=true` or
-	`core.fsmonitor=<hook_command_pathname>` (see
+	`core.fsmonitor=<hook-command-pathname>` (see
 	linkgit:git-update-index[1]): enable both the untracked cache
 	and FSMonitor features and only search directories that have
 	been modified since the previous `git status` command.  This
diff --git a/Documentation/git-submodule.txt b/Documentation/git-submodule.txt
index 6957306..ca0347a 100644
--- a/Documentation/git-submodule.txt
+++ b/Documentation/git-submodule.txt
@@ -136,7 +136,7 @@
 that use linkgit:git-rm[1] instead. See linkgit:gitsubmodules[7] for removal
 options.
 
-update [--init] [--remote] [-N|--no-fetch] [--[no-]recommend-shallow] [-f|--force] [--checkout|--rebase|--merge] [--reference <repository>] [--depth <depth>] [--recursive] [--jobs <n>] [--[no-]single-branch] [--filter <filter spec>] [--] [<path>...]::
+update [--init] [--remote] [-N|--no-fetch] [--[no-]recommend-shallow] [-f|--force] [--checkout|--rebase|--merge] [--reference <repository>] [--depth <depth>] [--recursive] [--jobs <n>] [--[no-]single-branch] [--filter <filter-spec>] [--] [<path>...]::
 +
 --
 Update the registered submodules to match what the superproject
@@ -185,7 +185,7 @@
 If `--recursive` is specified, this command will recurse into the
 registered submodules, and update any nested submodules within.
 
-If `--filter <filter spec>` is specified, the given partial clone filter will be
+If `--filter <filter-spec>` is specified, the given partial clone filter will be
 applied to the submodule. See linkgit:git-rev-list[1] for details on filter
 specifications.
 --
diff --git a/Documentation/git-svn.txt b/Documentation/git-svn.txt
index 4e92308..43c68c2 100644
--- a/Documentation/git-svn.txt
+++ b/Documentation/git-svn.txt
@@ -37,12 +37,12 @@
 	argument.  Normally this command initializes the current
 	directory.
 
--T<trunk_subdir>;;
---trunk=<trunk_subdir>;;
--t<tags_subdir>;;
---tags=<tags_subdir>;;
--b<branches_subdir>;;
---branches=<branches_subdir>;;
+-T<trunk-subdir>;;
+--trunk=<trunk-subdir>;;
+-t<tags-subdir>;;
+--tags=<tags-subdir>;;
+-b<branches-subdir>;;
+--branches=<branches-subdir>;;
 -s;;
 --stdlayout;;
 	These are optional command-line options for init.  Each of
@@ -726,9 +726,9 @@
 	when tracking a single URL.  The 'log' and 'dcommit' commands
 	no longer require this switch as an argument.
 
--R<remote name>::
---svn-remote <remote name>::
-	Specify the [svn-remote "<remote name>"] section to use,
+-R<remote-name>::
+--svn-remote <remote-name>::
+	Specify the [svn-remote "<remote-name>"] section to use,
 	this allows SVN multiple repositories to be tracked.
 	Default: "svn"
 
diff --git a/Documentation/git-switch.txt b/Documentation/git-switch.txt
index 3e23a82..f38e4c8 100644
--- a/Documentation/git-switch.txt
+++ b/Documentation/git-switch.txt
@@ -59,13 +59,18 @@
 -c <new-branch>::
 --create <new-branch>::
 	Create a new branch named `<new-branch>` starting at
-	`<start-point>` before switching to the branch. This is a
-	convenient shortcut for:
+	`<start-point>` before switching to the branch. This is the
+	transactional equivalent of
 +
 ------------
 $ git branch <new-branch>
 $ git switch <new-branch>
 ------------
++
+that is to say, the branch is not reset/created unless "git switch" is
+successful (e.g., when the branch is in use in another worktree, not
+just the current branch stays the same, but the branch is not reset to
+the start-point, either).
 
 -C <new-branch>::
 --force-create <new-branch>::
diff --git a/Documentation/git-tag.txt b/Documentation/git-tag.txt
index d42efb3..5fe519c 100644
--- a/Documentation/git-tag.txt
+++ b/Documentation/git-tag.txt
@@ -224,7 +224,7 @@
 
 -------------------------------------
 [user]
-    signingKey = <gpg-key_id>
+    signingKey = <gpg-key-id>
 -------------------------------------
 
 `pager.tag` is only respected when listing tags, i.e., when `-l` is
diff --git a/Documentation/git.txt b/Documentation/git.txt
index 962887f..0d25224 100644
--- a/Documentation/git.txt
+++ b/Documentation/git.txt
@@ -202,7 +202,7 @@
 	Do not perform optional operations that require locks. This is
 	equivalent to setting the `GIT_OPTIONAL_LOCKS` to `0`.
 
---list-cmds=group[,group...]::
+--list-cmds=<group>[,<group>...]::
 	List commands by group. This is an internal/experimental
 	option and may change or be removed in the future. Supported
 	groups are: builtins, parseopt (builtin commands that use
@@ -556,6 +556,11 @@
 	is always used. The default is "sha1".
 	See `--object-format` in linkgit:git-init[1].
 
+`GIT_DEFAULT_REF_FORMAT`::
+	If this variable is set, the default reference backend format for new
+	repositories will be set to this value. The default is "files".
+	See `--ref-format` in linkgit:git-init[1].
+
 Git Commits
 ~~~~~~~~~~~
 `GIT_AUTHOR_NAME`::
@@ -837,7 +842,7 @@
 collisions).
 +
 In addition, if the variable is set to
-`af_unix:[<socket_type>:]<absolute-pathname>`, Git will try
+`af_unix:[<socket-type>:]<absolute-pathname>`, Git will try
 to open the path as a Unix Domain Socket.  The socket type
 can be either `stream` or `dgram`.
 +
diff --git a/Documentation/gitattributes.txt b/Documentation/gitattributes.txt
index 8c1793c..4338d02 100644
--- a/Documentation/gitattributes.txt
+++ b/Documentation/gitattributes.txt
@@ -100,6 +100,21 @@
 the name of the attribute prefixed with an exclamation point `!`.
 
 
+RESERVED BUILTIN_* ATTRIBUTES
+-----------------------------
+
+builtin_* is a reserved namespace for builtin attribute values. Any
+user defined attributes under this namespace will be ignored and
+trigger a warning.
+
+`builtin_objectmode`
+~~~~~~~~~~~~~~~~~~~~
+This attribute is for filtering files by their file bit modes (40000,
+120000, 160000, 100755, 100644). e.g. ':(attr:builtin_objectmode=160000)'.
+You may also check these values with `git check-attr builtin_objectmode -- <file>`.
+If the object is not in the index `git check-attr --cached` will return unspecified.
+
+
 EFFECTS
 -------
 
@@ -1122,11 +1137,11 @@
 name.
 
 The `merge.*.driver` variable's value is used to construct a
-command to run to merge ancestor's version (`%O`), current
+command to run to common ancestor's version (`%O`), current
 version (`%A`) and the other branches' version (`%B`).  These
 three tokens are replaced with the names of temporary files that
 hold the contents of these versions when the command line is
-built. Additionally, %L will be replaced with the conflict marker
+built. Additionally, `%L` will be replaced with the conflict marker
 size (see below).
 
 The merge driver is expected to leave the result of the merge in
@@ -1144,8 +1159,9 @@
 internal merge and the final merge.
 
 The merge driver can learn the pathname in which the merged result
-will be stored via placeholder `%P`.
-
+will be stored via placeholder `%P`. The conflict labels to be used
+for the common ancestor, local head and other head can be passed by
+using '%S', '%X' and '%Y` respectively.
 
 `conflict-marker-size`
 ^^^^^^^^^^^^^^^^^^^^^^
diff --git a/Documentation/gitdiffcore.txt b/Documentation/gitdiffcore.txt
index 3cda2e0..642c512 100644
--- a/Documentation/gitdiffcore.txt
+++ b/Documentation/gitdiffcore.txt
@@ -245,20 +245,20 @@
 
 This transformation limits the set of filepairs to those that change
 specified strings between the preimage and the postimage in a certain
-way.  -S<block of text> and -G<regular expression> options are used to
+way.  -S<block-of-text> and -G<regular-expression> options are used to
 specify different ways these strings are sought.
 
-"-S<block of text>" detects filepairs whose preimage and postimage
+"-S<block-of-text>" detects filepairs whose preimage and postimage
 have different number of occurrences of the specified block of text.
 By definition, it will not detect in-file moves.  Also, when a
 changeset moves a file wholesale without affecting the interesting
 string, diffcore-rename kicks in as usual, and `-S` omits the filepair
 (since the number of occurrences of that string didn't change in that
 rename-detected filepair).  When used with `--pickaxe-regex`, treat
-the <block of text> as an extended POSIX regular expression to match,
+the <block-of-text> as an extended POSIX regular expression to match,
 instead of a literal string.
 
-"-G<regular expression>" (mnemonic: grep) detects filepairs whose
+"-G<regular-expression>" (mnemonic: grep) detects filepairs whose
 textual diff has an added or a deleted line that matches the given
 regular expression.  This means that it will detect in-file (or what
 rename-detection considers the same file) moves, which is noise.  The
diff --git a/Documentation/gitformat-index.txt b/Documentation/gitformat-index.txt
index 0773e5c..145cace 100644
--- a/Documentation/gitformat-index.txt
+++ b/Documentation/gitformat-index.txt
@@ -386,8 +386,8 @@
 	long, "REUC" extension that is M-bytes long, followed by "EOIE",
 	then the hash would be:
 
-	Hash("TREE" + <binary representation of N> +
-		"REUC" + <binary representation of M>)
+	Hash("TREE" + <binary-representation-of-N> +
+		"REUC" + <binary-representation-of-M>)
 
 == Index Entry Offset Table
 
diff --git a/Documentation/gitformat-pack.txt b/Documentation/gitformat-pack.txt
index 9fcb29a..d6ae229 100644
--- a/Documentation/gitformat-pack.txt
+++ b/Documentation/gitformat-pack.txt
@@ -396,6 +396,15 @@
 	    is padded at the end with between 0 and 3 NUL bytes to make the
 	    chunk size a multiple of 4 bytes.
 
+	Bitmapped Packfiles (ID: {'B', 'T', 'M', 'P'})
+	    Stores a table of two 4-byte unsigned integers in network order.
+	    Each table entry corresponds to a single pack (in the order that
+	    they appear above in the `PNAM` chunk). The values for each table
+	    entry are as follows:
+	    - The first bit position (in pseudo-pack order, see below) to
+	      contain an object from that pack.
+	    - The number of bits whose objects are selected from that pack.
+
 	OID Fanout (ID: {'O', 'I', 'D', 'F'})
 	    The ith entry, F[i], stores the number of OIDs with first
 	    byte at most i. Thus F[255] stores the total
@@ -509,6 +518,73 @@
 The MIDX's reverse index is stored in the optional 'RIDX' chunk within
 the MIDX itself.
 
+=== `BTMP` chunk
+
+The Bitmapped Packfiles (`BTMP`) chunk encodes additional information
+about the objects in the multi-pack index's reachability bitmap. Recall
+that objects from the MIDX are arranged in "pseudo-pack" order (see
+above) for reachability bitmaps.
+
+From the example above, suppose we have packs "a", "b", and "c", with
+10, 15, and 20 objects, respectively. In pseudo-pack order, those would
+be arranged as follows:
+
+    |a,0|a,1|...|a,9|b,0|b,1|...|b,14|c,0|c,1|...|c,19|
+
+When working with single-pack bitmaps (or, equivalently, multi-pack
+reachability bitmaps with a preferred pack), linkgit:git-pack-objects[1]
+performs ``verbatim'' reuse, attempting to reuse chunks of the bitmapped
+or preferred packfile instead of adding objects to the packing list.
+
+When a chunk of bytes is reused from an existing pack, any objects
+contained therein do not need to be added to the packing list, saving
+memory and CPU time. But a chunk from an existing packfile can only be
+reused when the following conditions are met:
+
+  - The chunk contains only objects which were requested by the caller
+    (i.e. does not contain any objects which the caller didn't ask for
+    explicitly or implicitly).
+
+  - All objects stored in non-thin packs as offset- or reference-deltas
+    also include their base object in the resulting pack.
+
+The `BTMP` chunk encodes the necessary information in order to implement
+multi-pack reuse over a set of packfiles as described above.
+Specifically, the `BTMP` chunk encodes three pieces of information (all
+32-bit unsigned integers in network byte-order) for each packfile `p`
+that is stored in the MIDX, as follows:
+
+`bitmap_pos`:: The first bit position (in pseudo-pack order) in the
+  multi-pack index's reachability bitmap occupied by an object from `p`.
+
+`bitmap_nr`:: The number of bit positions (including the one at
+  `bitmap_pos`) that encode objects from that pack `p`.
+
+For example, the `BTMP` chunk corresponding to the above example (with
+packs ``a'', ``b'', and ``c'') would look like:
+
+[cols="1,2,2"]
+|===
+| |`bitmap_pos` |`bitmap_nr`
+
+|packfile ``a''
+|`0`
+|`10`
+
+|packfile ``b''
+|`10`
+|`15`
+
+|packfile ``c''
+|`25`
+|`20`
+|===
+
+With this information in place, we can treat each packfile as
+individually reusable in the same fashion as verbatim pack reuse is
+performed on individual packs prior to the implementation of the `BTMP`
+chunk.
+
 == cruft packs
 
 The cruft packs feature offer an alternative to Git's traditional mechanism of
diff --git a/Documentation/githooks.txt b/Documentation/githooks.txt
index 883982e..37f91d5 100644
--- a/Documentation/githooks.txt
+++ b/Documentation/githooks.txt
@@ -243,7 +243,7 @@
 Information about what is to be pushed is provided on the hook's standard
 input with lines of the form:
 
-  <local ref> SP <local object name> SP <remote ref> SP <remote object name> LF
+  <local-ref> SP <local-object-name> SP <remote-ref> SP <remote-object-name> LF
 
 For instance, if the command +git push origin master:foreign+ were run the
 hook would receive a line like the following:
@@ -251,9 +251,9 @@
   refs/heads/master 67890 refs/heads/foreign 12345
 
 although the full object name would be supplied.  If the foreign ref does not
-yet exist the `<remote object name>` will be the all-zeroes object name.  If a
-ref is to be deleted, the `<local ref>` will be supplied as `(delete)` and the
-`<local object name>` will be the all-zeroes object name.  If the local commit
+yet exist the `<remote-object-name>` will be the all-zeroes object name.  If a
+ref is to be deleted, the `<local-ref>` will be supplied as `(delete)` and the
+`<local-object-name>` will be the all-zeroes object name.  If the local commit
 was specified by something other than a name which could be expanded (such as
 `HEAD~`, or an object name) it will be supplied as it was originally given.
 
diff --git a/Documentation/gitk.txt b/Documentation/gitk.txt
index c2213bb..35b3996 100644
--- a/Documentation/gitk.txt
+++ b/Documentation/gitk.txt
@@ -8,7 +8,7 @@
 SYNOPSIS
 --------
 [verse]
-'gitk' [<options>] [<revision range>] [--] [<path>...]
+'gitk' [<options>] [<revision-range>] [--] [<path>...]
 
 DESCRIPTION
 -----------
@@ -124,7 +124,7 @@
 	range to show.  The command is expected to print on its
 	standard output a list of additional revisions to be shown,
 	one per line.  Use this instead of explicitly specifying a
-	'<revision range>' if the set of commits to show may vary
+	'<revision-range>' if the set of commits to show may vary
 	between refreshes.
 
 --select-commit=<ref>::
diff --git a/Documentation/gitprotocol-capabilities.txt b/Documentation/gitprotocol-capabilities.txt
index d6c6eff..2cf7735 100644
--- a/Documentation/gitprotocol-capabilities.txt
+++ b/Documentation/gitprotocol-capabilities.txt
@@ -378,7 +378,7 @@
 or partial fetch and request that the server omit various objects
 from the packfile.
 
-session-id=<session id>
+session-id=<session-id>
 -----------------------
 
 The server may advertise a session ID that can be used to identify this process
diff --git a/Documentation/gitprotocol-http.txt b/Documentation/gitprotocol-http.txt
index 836b349..ec40a55 100644
--- a/Documentation/gitprotocol-http.txt
+++ b/Documentation/gitprotocol-http.txt
@@ -391,14 +391,14 @@
 
 C: Send one `$GIT_URL/git-upload-pack` request:
 
-   C: 0032want <want #1>...............................
-   C: 0032want <want #2>...............................
+   C: 0032want <want-#1>...............................
+   C: 0032want <want-#2>...............................
    ....
-   C: 0032have <common #1>.............................
-   C: 0032have <common #2>.............................
+   C: 0032have <common-#1>.............................
+   C: 0032have <common-#2>.............................
    ....
-   C: 0032have <have #1>...............................
-   C: 0032have <have #2>...............................
+   C: 0032have <have-#1>...............................
+   C: 0032have <have-#2>...............................
    ....
    C: 0000
 
@@ -512,7 +512,7 @@
 the id obtained through ref discovery as old_id.
 
   update_request  =  command_list
-		     "PACK" <binary data>
+		     "PACK" <binary-data>
 
   command_list    =  PKT-LINE(command NUL cap_list LF)
 		     *(command_pkt)
diff --git a/Documentation/gitprotocol-v2.txt b/Documentation/gitprotocol-v2.txt
index 8c1e7c6..0b800ab 100644
--- a/Documentation/gitprotocol-v2.txt
+++ b/Documentation/gitprotocol-v2.txt
@@ -199,7 +199,7 @@
 
 Additional features not supported in the base command will be advertised
 as the value of the command in the capability advertisement in the form
-of a space separated list of features: "<command>=<feature 1> <feature 2>"
+of a space separated list of features: "<command>=<feature-1> <feature-2>"
 
 ls-refs takes in the following arguments:
 
@@ -245,7 +245,7 @@
 
 Additional features not supported in the base command will be advertised
 as the value of the command in the capability advertisement in the form
-of a space separated list of features: "<command>=<feature 1> <feature 2>"
+of a space separated list of features: "<command>=<feature-1> <feature-2>"
 
 A `fetch` request can take the following arguments:
 
@@ -363,7 +363,7 @@
 addition of the 'packfile-uris' section in the server's response as
 explained below.
 
-    packfile-uris <comma-separated list of protocols>
+    packfile-uris <comma-separated-list-of-protocols>
 	Indicates to the server that the client is willing to receive
 	URIs of any of the given protocols in place of objects in the
 	sent packfile. Before performing the connectivity check, the
@@ -534,7 +534,7 @@
 only handle SHA-1.  If the client would like to use a hash algorithm other than
 SHA-1, it should specify its object-format string.
 
-session-id=<session id>
+session-id=<session-id>
 ~~~~~~~~~~~~~~~~~~~~~~~
 
 The server may advertise a session ID that can be used to identify this process
diff --git a/Documentation/gitsubmodules.txt b/Documentation/gitsubmodules.txt
index 8400d59..f7b5a25 100644
--- a/Documentation/gitsubmodules.txt
+++ b/Documentation/gitsubmodules.txt
@@ -151,7 +151,7 @@
 is not affected. This can be undone using `git submodule init`.
 
  * Deleted submodule: A submodule can be deleted by running
-`git rm <submodule path> && git commit`. This can be undone
+`git rm <submodule-path> && git commit`. This can be undone
 using `git revert`.
 +
 The deletion removes the superproject's tracking data, which are
@@ -229,7 +229,7 @@
   git submodule add <URL> <path>
 
   # Occasionally update the submodule to a new version:
-  git -C <path> checkout <new version>
+  git -C <path> checkout <new-version>
   git add <path>
   git commit -m "update submodule to new version"
 
diff --git a/Documentation/gitweb.conf.txt b/Documentation/gitweb.conf.txt
index 59fc1d2..8598358 100644
--- a/Documentation/gitweb.conf.txt
+++ b/Documentation/gitweb.conf.txt
@@ -343,7 +343,7 @@
 	Label for the "home link" at the top of all pages, leading to `$home_link`
 	(usually the main gitweb page, which contains the projects list).  It is
 	used as the first component of gitweb's "breadcrumb trail":
-	`<home link> / <project> / <action>`.  Can be set at build time using
+	`<home-link> / <project> / <action>`.  Can be set at build time using
 	the `GITWEB_HOME_LINK_STR` variable.  By default it is set to "projects",
 	as this link leads to the list of projects.  Another popular choice is to
 	set it to the name of site.  Note that it is treated as raw HTML so it
@@ -604,9 +604,9 @@
 Each `%feature` hash element is a hash reference and has the following
 structure:
 ----------------------------------------------------------------------
-"<feature_name>" => {
-	"sub" => <feature-sub (subroutine)>,
-	"override" => <allow-override (boolean)>,
+"<feature-name>" => {
+	"sub" => <feature-sub-(subroutine)>,
+	"override" => <allow-override-(boolean)>,
 	"default" => [ <options>... ]
 },
 ----------------------------------------------------------------------
@@ -614,7 +614,7 @@
 features the structure of appropriate `%feature` hash element has a simpler
 form:
 ----------------------------------------------------------------------
-"<feature_name>" => {
+"<feature-name>" => {
 	"override" => 0,
 	"default" => [ <options>... ]
 },
diff --git a/Documentation/gitweb.txt b/Documentation/gitweb.txt
index ddd4a0f..56d24a3 100644
--- a/Documentation/gitweb.txt
+++ b/Documentation/gitweb.txt
@@ -305,7 +305,7 @@
 looks like this:
 
 -----------------------------------------------------------------------
-.../gitweb.cgi/<repo>/<action>/<revision_from>:/<path_from>..<revision_to>:/<path_to>?<arguments>
+.../gitweb.cgi/<repo>/<action>/<revision-from>:/<path-from>..<revision-to>:/<path-to>?<arguments>
 -----------------------------------------------------------------------
 
 
diff --git a/Documentation/glossary-content.txt b/Documentation/glossary-content.txt
index f7d98c1..d71b199 100644
--- a/Documentation/glossary-content.txt
+++ b/Documentation/glossary-content.txt
@@ -638,6 +638,20 @@
 	An <<def_object,object>> used to temporarily store the contents of a
 	<<def_dirty,dirty>> working directory and the index for future reuse.
 
+[[def_special_ref]]special ref::
+	A ref that has different semantics than normal refs. These refs can be
+	accessed via normal Git commands but may not behave the same as a
+	normal ref in some cases.
++
+The following special refs are known to Git:
+
+ - "`FETCH_HEAD`" is written by linkgit:git-fetch[1] or linkgit:git-pull[1]. It
+   may refer to multiple object IDs. Each object ID is annotated with metadata
+   indicating where it was fetched from and its fetch status.
+
+ - "`MERGE_HEAD`" is written by linkgit:git-merge[1] when resolving merge
+   conflicts. It contains all commit IDs which are being merged.
+
 [[def_submodule]]submodule::
 	A <<def_repository,repository>> that holds the history of a
 	separate project inside another repository (the latter of
diff --git a/Documentation/ref-storage-format.txt b/Documentation/ref-storage-format.txt
new file mode 100644
index 0000000..1a65cac
--- /dev/null
+++ b/Documentation/ref-storage-format.txt
@@ -0,0 +1 @@
+* `files` for loose files with packed-refs. This is the default.
diff --git a/Documentation/technical/repository-version.txt b/Documentation/technical/repository-version.txt
index 045a767..27be374 100644
--- a/Documentation/technical/repository-version.txt
+++ b/Documentation/technical/repository-version.txt
@@ -100,3 +100,8 @@
 multiple working directory mode, "config" file is shared while
 "config.worktree" is per-working directory (i.e., it's in
 GIT_COMMON_DIR/worktrees/<id>/config.worktree)
+
+==== `refStorage`
+
+Specifies the file format for the ref database. The only valid value
+is `files` (loose references with a packed-refs file).
diff --git a/Documentation/technical/unit-tests.txt b/Documentation/technical/unit-tests.txt
new file mode 100644
index 0000000..206037f
--- /dev/null
+++ b/Documentation/technical/unit-tests.txt
@@ -0,0 +1,240 @@
+= Unit Testing
+
+In our current testing environment, we spend a significant amount of effort
+crafting end-to-end tests for error conditions that could easily be captured by
+unit tests (or we simply forgo some hard-to-setup and rare error conditions).
+Unit tests additionally provide stability to the codebase and can simplify
+debugging through isolation. Writing unit tests in pure C, rather than with our
+current shell/test-tool helper setup, simplifies test setup, simplifies passing
+data around (no shell-isms required), and reduces testing runtime by not
+spawning a separate process for every test invocation.
+
+We believe that a large body of unit tests, living alongside the existing test
+suite, will improve code quality for the Git project.
+
+== Definitions
+
+For the purposes of this document, we'll use *test framework* to refer to
+projects that support writing test cases and running tests within the context
+of a single executable. *Test harness* will refer to projects that manage
+running multiple executables (each of which may contain multiple test cases) and
+aggregating their results.
+
+In reality, these terms are not strictly defined, and many of the projects
+discussed below contain features from both categories.
+
+For now, we will evaluate projects solely on their framework features. Since we
+are relying on having TAP output (see below), we can assume that any framework
+can be made to work with a harness that we can choose later.
+
+
+== Summary
+
+We believe the best way forward is to implement a custom TAP framework for the
+Git project. We use a version of the framework originally proposed in
+https://lore.kernel.org/git/c902a166-98ce-afba-93f2-ea6027557176@gmail.com/[1].
+
+See the <<framework-selection,Framework Selection>> section below for the
+rationale behind this decision.
+
+
+== Choosing a test harness
+
+During upstream discussion, it was occasionally noted that `prove` provides many
+convenient features, such as scheduling slower tests first, or re-running
+previously failed tests.
+
+While we already support the use of `prove` as a test harness for the shell
+tests, it is not strictly required. The t/Makefile allows running shell tests
+directly (though with interleaved output if parallelism is enabled). Git
+developers who wish to use `prove` as a more advanced harness can do so by
+setting DEFAULT_TEST_TARGET=prove in their config.mak.
+
+We will follow a similar approach for unit tests: by default the test
+executables will be run directly from the t/Makefile, but `prove` can be
+configured with DEFAULT_UNIT_TEST_TARGET=prove.
+
+
+[[framework-selection]]
+== Framework selection
+
+There are a variety of features we can use to rank the candidate frameworks, and
+those features have different priorities:
+
+* Critical features: we probably won't consider a framework without these
+** Can we legally / easily use the project?
+*** <<license,License>>
+*** <<vendorable-or-ubiquitous,Vendorable or ubiquitous>>
+*** <<maintainable-extensible,Maintainable / extensible>>
+*** <<major-platform-support,Major platform support>>
+** Does the project support our bare-minimum needs?
+*** <<tap-support,TAP support>>
+*** <<diagnostic-output,Diagnostic output>>
+*** <<runtime-skippable-tests,Runtime-skippable tests>>
+* Nice-to-have features:
+** <<parallel-execution,Parallel execution>>
+** <<mock-support,Mock support>>
+** <<signal-error-handling,Signal & error-handling>>
+* Tie-breaker stats
+** <<project-kloc,Project KLOC>>
+** <<adoption,Adoption>>
+
+[[license]]
+=== License
+
+We must be able to legally use the framework in connection with Git. As Git is
+licensed only under GPLv2, we must eliminate any LGPLv3, GPLv3, or Apache 2.0
+projects.
+
+[[vendorable-or-ubiquitous]]
+=== Vendorable or ubiquitous
+
+We want to avoid forcing Git developers to install new tools just to run unit
+tests. Any prospective frameworks and harnesses must either be vendorable
+(meaning, we can copy their source directly into Git's repository), or so
+ubiquitous that it is reasonable to expect that most developers will have the
+tools installed already.
+
+[[maintainable-extensible]]
+=== Maintainable / extensible
+
+It is unlikely that any pre-existing project perfectly fits our needs, so any
+project we select will need to be actively maintained and open to accepting
+changes. Alternatively, assuming we are vendoring the source into our repo, it
+must be simple enough that Git developers can feel comfortable making changes as
+needed to our version.
+
+In the comparison table below, "True" means that the framework seems to have
+active developers, that it is simple enough that Git developers can make changes
+to it, and that the project seems open to accepting external contributions (or
+that it is vendorable). "Partial" means that at least one of the above
+conditions holds.
+
+[[major-platform-support]]
+=== Major platform support
+
+At a bare minimum, unit-testing must work on Linux, MacOS, and Windows.
+
+In the comparison table below, "True" means that it works on all three major
+platforms with no issues. "Partial" means that there may be annoyances on one or
+more platforms, but it is still usable in principle.
+
+[[tap-support]]
+=== TAP support
+
+The https://testanything.org/[Test Anything Protocol] is a text-based interface
+that allows tests to communicate with a test harness. It is already used by
+Git's integration test suite. Supporting TAP output is a mandatory feature for
+any prospective test framework.
+
+In the comparison table below, "True" means this is natively supported.
+"Partial" means TAP output must be generated by post-processing the native
+output.
+
+Frameworks that do not have at least Partial support will not be evaluated
+further.
+
+[[diagnostic-output]]
+=== Diagnostic output
+
+When a test case fails, the framework must generate enough diagnostic output to
+help developers find the appropriate test case in source code in order to debug
+the failure.
+
+[[runtime-skippable-tests]]
+=== Runtime-skippable tests
+
+Test authors may wish to skip certain test cases based on runtime circumstances,
+so the framework should support this.
+
+[[parallel-execution]]
+=== Parallel execution
+
+Ideally, we will build up a significant collection of unit test cases, most
+likely split across multiple executables. It will be necessary to run these
+tests in parallel to enable fast develop-test-debug cycles.
+
+In the comparison table below, "True" means that individual test cases within a
+single test executable can be run in parallel. We assume that executable-level
+parallelism can be handled by the test harness.
+
+[[mock-support]]
+=== Mock support
+
+Unit test authors may wish to test code that interacts with objects that may be
+inconvenient to handle in a test (e.g. interacting with a network service).
+Mocking allows test authors to provide a fake implementation of these objects
+for more convenient tests.
+
+[[signal-error-handling]]
+=== Signal & error handling
+
+The test framework should fail gracefully when test cases are themselves buggy
+or when they are interrupted by signals during runtime.
+
+[[project-kloc]]
+=== Project KLOC
+
+The size of the project, in thousands of lines of code as measured by
+https://dwheeler.com/sloccount/[sloccount] (rounded up to the next multiple of
+1,000). As a tie-breaker, we probably prefer a project with fewer LOC.
+
+[[adoption]]
+=== Adoption
+
+As a tie-breaker, we prefer a more widely-used project. We use the number of
+GitHub / GitLab stars to estimate this.
+
+
+=== Comparison
+
+:true: [lime-background]#True#
+:false: [red-background]#False#
+:partial: [yellow-background]#Partial#
+
+:gpl: [lime-background]#GPL v2#
+:isc: [lime-background]#ISC#
+:mit: [lime-background]#MIT#
+:expat: [lime-background]#Expat#
+:lgpl: [lime-background]#LGPL v2.1#
+
+:custom-impl: https://lore.kernel.org/git/c902a166-98ce-afba-93f2-ea6027557176@gmail.com/[Custom Git impl.]
+:greatest: https://github.com/silentbicycle/greatest[Greatest]
+:criterion: https://github.com/Snaipe/Criterion[Criterion]
+:c-tap: https://github.com/rra/c-tap-harness/[C TAP]
+:check: https://libcheck.github.io/check/[Check]
+
+[format="csv",options="header",width="33%",subs="specialcharacters,attributes,quotes,macros"]
+|=====
+Framework,"<<license,License>>","<<vendorable-or-ubiquitous,Vendorable or ubiquitous>>","<<maintainable-extensible,Maintainable / extensible>>","<<major-platform-support,Major platform support>>","<<tap-support,TAP support>>","<<diagnostic-output,Diagnostic output>>","<<runtime--skippable-tests,Runtime- skippable tests>>","<<parallel-execution,Parallel execution>>","<<mock-support,Mock support>>","<<signal-error-handling,Signal & error handling>>","<<project-kloc,Project KLOC>>","<<adoption,Adoption>>"
+{custom-impl},{gpl},{true},{true},{true},{true},{true},{true},{false},{false},{false},1,0
+{greatest},{isc},{true},{partial},{true},{partial},{true},{true},{false},{false},{false},3,1400
+{criterion},{mit},{false},{partial},{true},{true},{true},{true},{true},{false},{true},19,1800
+{c-tap},{expat},{true},{partial},{partial},{true},{false},{true},{false},{false},{false},4,33
+{check},{lgpl},{false},{partial},{true},{true},{true},{false},{false},{false},{true},17,973
+|=====
+
+=== Additional framework candidates
+
+Several suggested frameworks have been eliminated from consideration:
+
+* Incompatible licenses:
+** https://github.com/zorgnax/libtap[libtap] (LGPL v3)
+** https://cmocka.org/[cmocka] (Apache 2.0)
+* Missing source: https://www.kindahl.net/mytap/doc/index.html[MyTap]
+* No TAP support:
+** https://nemequ.github.io/munit/[µnit]
+** https://github.com/google/cmockery[cmockery]
+** https://github.com/lpabon/cmockery2[cmockery2]
+** https://github.com/ThrowTheSwitch/Unity[Unity]
+** https://github.com/siu/minunit[minunit]
+** https://cunit.sourceforge.net/[CUnit]
+
+
+== Milestones
+
+* Add useful tests of library-like code
+* Integrate with
+  https://lore.kernel.org/git/20230502211454.1673000-1-calvinwan@google.com/[stdlib
+  work]
+* Run alongside regular `make test` target
diff --git a/Documentation/trace2-target-values.txt b/Documentation/trace2-target-values.txt
index 3985b6d..06f1953 100644
--- a/Documentation/trace2-target-values.txt
+++ b/Documentation/trace2-target-values.txt
@@ -5,7 +5,7 @@
 * `<absolute-pathname>` - Writes to the file in append mode. If the target
 already exists and is a directory, the traces will be written to files (one
 per process) underneath the given directory.
-* `af_unix:[<socket_type>:]<absolute-pathname>` - Write to a
+* `af_unix:[<socket-type>:]<absolute-pathname>` - Write to a
 Unix DomainSocket (on platforms that support them).  Socket
 type can be either `stream` or `dgram`; if omitted Git will
 try both.
diff --git a/Documentation/urls.txt b/Documentation/urls.txt
index 4e79c15..ce671f8 100644
--- a/Documentation/urls.txt
+++ b/Documentation/urls.txt
@@ -73,8 +73,8 @@
 configuration section of the form:
 
 ------------
-	[url "<actual url base>"]
-		insteadOf = <other url base>
+	[url "<actual-url-base>"]
+		insteadOf = <other-url-base>
 ------------
 
 For example, with this:
@@ -92,8 +92,8 @@
 configuration section of the form:
 
 ------------
-	[url "<actual url base>"]
-		pushInsteadOf = <other url base>
+	[url "<actual-url-base>"]
+		pushInsteadOf = <other-url-base>
 ------------
 
 For example, with this:
diff --git a/Documentation/user-manual.txt b/Documentation/user-manual.txt
index 5d32ff2..6433903 100644
--- a/Documentation/user-manual.txt
+++ b/Documentation/user-manual.txt
@@ -4100,8 +4100,8 @@
 be validated by verifying that (a) their hashes match the content of the
 file and (b) the object successfully inflates to a stream of bytes that
 forms a sequence of
-`<ascii type without space> + <space> + <ascii decimal size> +
-<byte\0> + <binary object data>`.
+`<ascii-type-without-space> + <space> + <ascii-decimal-size> +
+<byte\0> + <binary-object-data>`.
 
 The structured objects can further have their structure and
 connectivity to other objects verified. This is generally done with
diff --git a/GIT-VERSION-GEN b/GIT-VERSION-GEN
index e1f223d..d3a33f0 100755
--- a/GIT-VERSION-GEN
+++ b/GIT-VERSION-GEN
@@ -1,7 +1,7 @@
 #!/bin/sh
 
 GVF=GIT-VERSION-FILE
-DEF_VER=v2.43.2
+DEF_VER=v2.44.0-rc1
 
 LF='
 '
@@ -11,7 +11,7 @@
 if test -f version
 then
 	VN=$(cat version) || VN="$DEF_VER"
-elif test -d ${GIT_DIR:-.git} -o -f .git &&
+elif { test -d "${GIT_DIR:-.git}" || test -f .git; } &&
 	VN=$(git describe --match "v[0-9]*" HEAD 2>/dev/null) &&
 	case "$VN" in
 	*$LF*) (exit 1) ;;
diff --git a/Makefile b/Makefile
index 1618ee2..78e8740 100644
--- a/Makefile
+++ b/Makefile
@@ -682,6 +682,9 @@
 TEST_OBJS =
 TEST_PROGRAMS_NEED_X =
 THIRD_PARTY_SOURCES =
+UNIT_TEST_PROGRAMS =
+UNIT_TEST_DIR = t/unit-tests
+UNIT_TEST_BIN = $(UNIT_TEST_DIR)/bin
 
 # Having this variable in your environment would break pipelines because
 # you cause "cd" to echo its destination to stdout.  It can also take
@@ -749,7 +752,12 @@
 
 ETAGS_TARGET = TAGS
 
+# If you add a new fuzzer, please also make sure to run it in
+# ci/run-build-and-minimal-fuzzers.sh so that we make sure it still links and
+# runs in the future.
+FUZZ_OBJS += oss-fuzz/dummy-cmd-main.o
 FUZZ_OBJS += oss-fuzz/fuzz-commit-graph.o
+FUZZ_OBJS += oss-fuzz/fuzz-date.o
 FUZZ_OBJS += oss-fuzz/fuzz-pack-headers.o
 FUZZ_OBJS += oss-fuzz/fuzz-pack-idx.o
 .PHONY: fuzz-objs
@@ -758,7 +766,7 @@
 # Always build fuzz objects even if not testing, to prevent bit-rot.
 all:: $(FUZZ_OBJS)
 
-FUZZ_PROGRAMS += $(patsubst %.o,%,$(FUZZ_OBJS))
+FUZZ_PROGRAMS += $(patsubst %.o,%,$(filter-out %dummy-cmd-main.o,$(FUZZ_OBJS)))
 
 # Empty...
 EXTRA_PROGRAMS =
@@ -788,7 +796,6 @@
 TEST_BUILTINS_OBJS += test-config.o
 TEST_BUILTINS_OBJS += test-crontab.o
 TEST_BUILTINS_OBJS += test-csprng.o
-TEST_BUILTINS_OBJS += test-ctype.o
 TEST_BUILTINS_OBJS += test-date.o
 TEST_BUILTINS_OBJS += test-delta.o
 TEST_BUILTINS_OBJS += test-dir-iterator.o
@@ -799,7 +806,6 @@
 TEST_BUILTINS_OBJS += test-dump-untracked-cache.o
 TEST_BUILTINS_OBJS += test-env-helper.o
 TEST_BUILTINS_OBJS += test-example-decorate.o
-TEST_BUILTINS_OBJS += test-fast-rebase.o
 TEST_BUILTINS_OBJS += test-find-pack.o
 TEST_BUILTINS_OBJS += test-fsmonitor-client.o
 TEST_BUILTINS_OBJS += test-genrandom.o
@@ -825,7 +831,6 @@
 TEST_BUILTINS_OBJS += test-path-utils.o
 TEST_BUILTINS_OBJS += test-pcre2-config.o
 TEST_BUILTINS_OBJS += test-pkt-line.o
-TEST_BUILTINS_OBJS += test-prio-queue.o
 TEST_BUILTINS_OBJS += test-proc-receive.o
 TEST_BUILTINS_OBJS += test-progress.o
 TEST_BUILTINS_OBJS += test-reach.o
@@ -1290,6 +1295,7 @@
 BUILTIN_OBJS += builtin/remote.o
 BUILTIN_OBJS += builtin/repack.o
 BUILTIN_OBJS += builtin/replace.o
+BUILTIN_OBJS += builtin/replay.o
 BUILTIN_OBJS += builtin/rerere.o
 BUILTIN_OBJS += builtin/reset.o
 BUILTIN_OBJS += builtin/rev-list.o
@@ -1335,6 +1341,15 @@
 THIRD_PARTY_SOURCES += sha1collisiondetection/%
 THIRD_PARTY_SOURCES += sha1dc/%
 
+UNIT_TEST_PROGRAMS += t-basic
+UNIT_TEST_PROGRAMS += t-mem-pool
+UNIT_TEST_PROGRAMS += t-strbuf
+UNIT_TEST_PROGRAMS += t-ctype
+UNIT_TEST_PROGRAMS += t-prio-queue
+UNIT_TEST_PROGS = $(patsubst %,$(UNIT_TEST_BIN)/%$X,$(UNIT_TEST_PROGRAMS))
+UNIT_TEST_OBJS = $(patsubst %,$(UNIT_TEST_DIR)/%.o,$(UNIT_TEST_PROGRAMS))
+UNIT_TEST_OBJS += $(UNIT_TEST_DIR)/test-lib.o
+
 # xdiff and reftable libs may in turn depend on what is in libgit.a
 GITLIBS = common-main.o $(LIB_FILE) $(XDIFF_LIB) $(REFTABLE_LIB) $(LIB_FILE)
 EXTLIBS =
@@ -1575,7 +1590,7 @@
 
 ifdef LIBPCREDIR
 	BASIC_CFLAGS += -I$(LIBPCREDIR)/include
-	EXTLIBS += -L$(LIBPCREDIR)/$(lib) $(CC_LD_DYNPATH)$(LIBPCREDIR)/$(lib)
+	EXTLIBS += $(call libpath_template,$(LIBPCREDIR)/$(lib))
 endif
 
 ifdef HAVE_ALLOCA_H
@@ -1595,7 +1610,7 @@
 	ifdef CURLDIR
 		# Try "-Wl,-rpath=$(CURLDIR)/$(lib)" in such a case.
 		CURL_CFLAGS = -I$(CURLDIR)/include
-		CURL_LIBCURL = -L$(CURLDIR)/$(lib) $(CC_LD_DYNPATH)$(CURLDIR)/$(lib)
+		CURL_LIBCURL = $(call libpath_template,$(CURLDIR)/$(lib))
 	else
 		CURL_CFLAGS =
 		CURL_LIBCURL =
@@ -1631,7 +1646,7 @@
 	ifndef NO_EXPAT
 		ifdef EXPATDIR
 			BASIC_CFLAGS += -I$(EXPATDIR)/include
-			EXPAT_LIBEXPAT = -L$(EXPATDIR)/$(lib) $(CC_LD_DYNPATH)$(EXPATDIR)/$(lib) -lexpat
+			EXPAT_LIBEXPAT = $(call libpath_template,$(EXPATDIR)/$(lib)) -lexpat
 		else
 			EXPAT_LIBEXPAT = -lexpat
 		endif
@@ -1644,7 +1659,7 @@
 
 ifdef ZLIB_PATH
 	BASIC_CFLAGS += -I$(ZLIB_PATH)/include
-	EXTLIBS += -L$(ZLIB_PATH)/$(lib) $(CC_LD_DYNPATH)$(ZLIB_PATH)/$(lib)
+	EXTLIBS += $(call libpath_template,$(ZLIB_PATH)/$(lib))
 endif
 EXTLIBS += -lz
 
@@ -1652,7 +1667,7 @@
 	OPENSSL_LIBSSL = -lssl
 	ifdef OPENSSLDIR
 		BASIC_CFLAGS += -I$(OPENSSLDIR)/include
-		OPENSSL_LINK = -L$(OPENSSLDIR)/$(lib) $(CC_LD_DYNPATH)$(OPENSSLDIR)/$(lib)
+		OPENSSL_LINK = $(call libpath_template,$(OPENSSLDIR)/$(lib))
 	else
 		OPENSSL_LINK =
 	endif
@@ -1679,7 +1694,7 @@
 	ifdef NEEDS_LIBICONV
 		ifdef ICONVDIR
 			BASIC_CFLAGS += -I$(ICONVDIR)/include
-			ICONV_LINK = -L$(ICONVDIR)/$(lib) $(CC_LD_DYNPATH)$(ICONVDIR)/$(lib)
+			ICONV_LINK = $(call libpath_template,$(ICONVDIR)/$(lib))
 		else
 			ICONV_LINK =
 		endif
@@ -2342,7 +2357,7 @@
 
 all:: $(ALL_COMMANDS_TO_INSTALL) $(SCRIPT_LIB) $(OTHER_PROGRAMS) GIT-BUILD-OPTIONS
 ifneq (,$X)
-	$(QUIET_BUILT_IN)$(foreach p,$(patsubst %$X,%,$(filter %$X,$(ALL_COMMANDS_TO_INSTALL) $(OTHER_PROGRAMS))), test -d '$p' -o '$p' -ef '$p$X' || $(RM) '$p';)
+	$(QUIET_BUILT_IN)$(foreach p,$(patsubst %$X,%,$(filter %$X,$(ALL_COMMANDS_TO_INSTALL) $(OTHER_PROGRAMS))), if test ! -d '$p' && test ! '$p' -ef '$p$X'; then $(RM) '$p'; fi;)
 endif
 
 all::
@@ -2676,6 +2691,7 @@
 OBJECTS += $(XDIFF_OBJS)
 OBJECTS += $(FUZZ_OBJS)
 OBJECTS += $(REFTABLE_OBJS) $(REFTABLE_TEST_OBJS)
+OBJECTS += $(UNIT_TEST_OBJS)
 
 ifndef NO_CURL
 	OBJECTS += http.o http-walker.o remote-curl.o
@@ -3178,7 +3194,7 @@
 
 test_bindir_programs := $(patsubst %,bin-wrappers/%,$(BINDIR_PROGRAMS_NEED_X) $(BINDIR_PROGRAMS_NO_X) $(TEST_PROGRAMS_NEED_X))
 
-all:: $(TEST_PROGRAMS) $(test_bindir_programs)
+all:: $(TEST_PROGRAMS) $(test_bindir_programs) $(UNIT_TEST_PROGS)
 
 bin-wrappers/%: wrap-for-bin.sh
 	$(call mkdir_p_parent_template)
@@ -3604,12 +3620,12 @@
 .PHONY: rpm
 
 ifneq ($(INCLUDE_DLLS_IN_ARTIFACTS),)
-OTHER_PROGRAMS += $(shell echo *.dll t/helper/*.dll)
+OTHER_PROGRAMS += $(shell echo *.dll t/helper/*.dll t/unit-tests/bin/*.dll)
 endif
 
 artifacts-tar:: $(ALL_COMMANDS_TO_INSTALL) $(SCRIPT_LIB) $(OTHER_PROGRAMS) \
 		GIT-BUILD-OPTIONS $(TEST_PROGRAMS) $(test_bindir_programs) \
-		$(MOFILES)
+		$(UNIT_TEST_PROGS) $(MOFILES)
 	$(QUIET_SUBDIR0)templates $(QUIET_SUBDIR1) \
 		SHELL_PATH='$(SHELL_PATH_SQ)' PERL_PATH='$(PERL_PATH_SQ)'
 	test -n "$(ARTIFACTS_DIRECTORY)"
@@ -3664,7 +3680,7 @@
 	$(RM) contrib/coccinelle/*.cocci.patch
 
 clean: profile-clean coverage-clean cocciclean
-	$(RM) -r .build
+	$(RM) -r .build $(UNIT_TEST_BIN)
 	$(RM) po/git.pot po/git-core.pot
 	$(RM) git.res
 	$(RM) $(OBJECTS)
@@ -3838,15 +3854,26 @@
 #
 # make CC=clang CXX=clang++ \
 #      CFLAGS="-fsanitize=fuzzer-no-link,address" \
-#      LIB_FUZZING_ENGINE="-fsanitize=fuzzer" \
+#      LIB_FUZZING_ENGINE="-fsanitize=fuzzer,address" \
 #      fuzz-all
 #
-FUZZ_CXXFLAGS ?= $(CFLAGS)
+FUZZ_CXXFLAGS ?= $(ALL_CFLAGS)
 
 .PHONY: fuzz-all
 
-$(FUZZ_PROGRAMS): all
-	$(QUIET_LINK)$(CXX) $(FUZZ_CXXFLAGS) $(LIB_OBJS) $(BUILTIN_OBJS) \
-		$(XDIFF_OBJS) $(EXTLIBS) git.o $@.o $(LIB_FUZZING_ENGINE) -o $@
+$(FUZZ_PROGRAMS): %: %.o oss-fuzz/dummy-cmd-main.o $(GITLIBS) GIT-LDFLAGS
+	$(QUIET_LINK)$(CXX) $(FUZZ_CXXFLAGS) -o $@ $(ALL_LDFLAGS) \
+		-Wl,--allow-multiple-definition \
+		$(filter %.o,$^) $(filter %.a,$^) $(LIBS) $(LIB_FUZZING_ENGINE)
 
 fuzz-all: $(FUZZ_PROGRAMS)
+
+$(UNIT_TEST_PROGS): $(UNIT_TEST_BIN)/%$X: $(UNIT_TEST_DIR)/%.o $(UNIT_TEST_DIR)/test-lib.o $(GITLIBS) GIT-LDFLAGS
+	$(call mkdir_p_parent_template)
+	$(QUIET_LINK)$(CC) $(ALL_CFLAGS) -o $@ $(ALL_LDFLAGS) \
+		$(filter %.o,$^) $(filter %.a,$^) $(LIBS)
+
+.PHONY: build-unit-tests unit-tests
+build-unit-tests: $(UNIT_TEST_PROGS)
+unit-tests: $(UNIT_TEST_PROGS)
+	$(MAKE) -C t/ unit-tests
diff --git a/RelNotes b/RelNotes
index 9ceb8d9..a55478f 120000
--- a/RelNotes
+++ b/RelNotes
@@ -1 +1 @@
-Documentation/RelNotes/2.43.2.txt
\ No newline at end of file
+Documentation/RelNotes/2.44.0.txt
\ No newline at end of file
diff --git a/advice.c b/advice.c
index 50c7944..6e9098f 100644
--- a/advice.c
+++ b/advice.c
@@ -33,52 +33,56 @@ static const char *advise_get_color(enum color_advice ix)
 	return "";
 }
 
+enum advice_level {
+	ADVICE_LEVEL_NONE = 0,
+	ADVICE_LEVEL_DISABLED,
+	ADVICE_LEVEL_ENABLED,
+};
+
 static struct {
 	const char *key;
-	int enabled;
+	enum advice_level level;
 } advice_setting[] = {
-	[ADVICE_ADD_EMBEDDED_REPO]			= { "addEmbeddedRepo", 1 },
-	[ADVICE_ADD_EMPTY_PATHSPEC]			= { "addEmptyPathspec", 1 },
-	[ADVICE_ADD_IGNORED_FILE]			= { "addIgnoredFile", 1 },
-	[ADVICE_AM_WORK_DIR] 				= { "amWorkDir", 1 },
-	[ADVICE_AMBIGUOUS_FETCH_REFSPEC]		= { "ambiguousFetchRefspec", 1 },
-	[ADVICE_CHECKOUT_AMBIGUOUS_REMOTE_BRANCH_NAME] 	= { "checkoutAmbiguousRemoteBranchName", 1 },
-	[ADVICE_COMMIT_BEFORE_MERGE]			= { "commitBeforeMerge", 1 },
-	[ADVICE_DETACHED_HEAD]				= { "detachedHead", 1 },
-	[ADVICE_SUGGEST_DETACHING_HEAD]			= { "suggestDetachingHead", 1 },
-	[ADVICE_DIVERGING]				= { "diverging", 1 },
-	[ADVICE_FETCH_SHOW_FORCED_UPDATES]		= { "fetchShowForcedUpdates", 1 },
-	[ADVICE_GRAFT_FILE_DEPRECATED]			= { "graftFileDeprecated", 1 },
-	[ADVICE_IGNORED_HOOK]				= { "ignoredHook", 1 },
-	[ADVICE_IMPLICIT_IDENTITY]			= { "implicitIdentity", 1 },
-	[ADVICE_NESTED_TAG]				= { "nestedTag", 1 },
-	[ADVICE_OBJECT_NAME_WARNING]			= { "objectNameWarning", 1 },
-	[ADVICE_PUSH_ALREADY_EXISTS]			= { "pushAlreadyExists", 1 },
-	[ADVICE_PUSH_FETCH_FIRST]			= { "pushFetchFirst", 1 },
-	[ADVICE_PUSH_NEEDS_FORCE]			= { "pushNeedsForce", 1 },
-	[ADVICE_PUSH_REF_NEEDS_UPDATE]			= { "pushRefNeedsUpdate", 1 },
-
-	/* make this an alias for backward compatibility */
-	[ADVICE_PUSH_UPDATE_REJECTED_ALIAS]		= { "pushNonFastForward", 1 },
-
-	[ADVICE_PUSH_NON_FF_CURRENT]			= { "pushNonFFCurrent", 1 },
-	[ADVICE_PUSH_NON_FF_MATCHING]			= { "pushNonFFMatching", 1 },
-	[ADVICE_PUSH_UNQUALIFIED_REF_NAME]		= { "pushUnqualifiedRefName", 1 },
-	[ADVICE_PUSH_UPDATE_REJECTED]			= { "pushUpdateRejected", 1 },
-	[ADVICE_RESET_NO_REFRESH_WARNING]		= { "resetNoRefresh", 1 },
-	[ADVICE_RESOLVE_CONFLICT]			= { "resolveConflict", 1 },
-	[ADVICE_RM_HINTS]				= { "rmHints", 1 },
-	[ADVICE_SEQUENCER_IN_USE]			= { "sequencerInUse", 1 },
-	[ADVICE_SET_UPSTREAM_FAILURE]			= { "setUpstreamFailure", 1 },
-	[ADVICE_SKIPPED_CHERRY_PICKS]			= { "skippedCherryPicks", 1 },
-	[ADVICE_STATUS_AHEAD_BEHIND_WARNING]		= { "statusAheadBehindWarning", 1 },
-	[ADVICE_STATUS_HINTS]				= { "statusHints", 1 },
-	[ADVICE_STATUS_U_OPTION]			= { "statusUoption", 1 },
-	[ADVICE_SUBMODULE_ALTERNATE_ERROR_STRATEGY_DIE] = { "submoduleAlternateErrorStrategyDie", 1 },
-	[ADVICE_SUBMODULES_NOT_UPDATED] 		= { "submodulesNotUpdated", 1 },
-	[ADVICE_UPDATE_SPARSE_PATH]			= { "updateSparsePath", 1 },
-	[ADVICE_WAITING_FOR_EDITOR]			= { "waitingForEditor", 1 },
-	[ADVICE_WORKTREE_ADD_ORPHAN]			= { "worktreeAddOrphan", 1 },
+	[ADVICE_ADD_EMBEDDED_REPO]			= { "addEmbeddedRepo" },
+	[ADVICE_ADD_EMPTY_PATHSPEC]			= { "addEmptyPathspec" },
+	[ADVICE_ADD_IGNORED_FILE]			= { "addIgnoredFile" },
+	[ADVICE_AMBIGUOUS_FETCH_REFSPEC]		= { "ambiguousFetchRefspec" },
+	[ADVICE_AM_WORK_DIR] 				= { "amWorkDir" },
+	[ADVICE_CHECKOUT_AMBIGUOUS_REMOTE_BRANCH_NAME] 	= { "checkoutAmbiguousRemoteBranchName" },
+	[ADVICE_COMMIT_BEFORE_MERGE]			= { "commitBeforeMerge" },
+	[ADVICE_DETACHED_HEAD]				= { "detachedHead" },
+	[ADVICE_DIVERGING]				= { "diverging" },
+	[ADVICE_FETCH_SHOW_FORCED_UPDATES]		= { "fetchShowForcedUpdates" },
+	[ADVICE_FORCE_DELETE_BRANCH]			= { "forceDeleteBranch" },
+	[ADVICE_GRAFT_FILE_DEPRECATED]			= { "graftFileDeprecated" },
+	[ADVICE_IGNORED_HOOK]				= { "ignoredHook" },
+	[ADVICE_IMPLICIT_IDENTITY]			= { "implicitIdentity" },
+	[ADVICE_NESTED_TAG]				= { "nestedTag" },
+	[ADVICE_OBJECT_NAME_WARNING]			= { "objectNameWarning" },
+	[ADVICE_PUSH_ALREADY_EXISTS]			= { "pushAlreadyExists" },
+	[ADVICE_PUSH_FETCH_FIRST]			= { "pushFetchFirst" },
+	[ADVICE_PUSH_NEEDS_FORCE]			= { "pushNeedsForce" },
+	[ADVICE_PUSH_NON_FF_CURRENT]			= { "pushNonFFCurrent" },
+	[ADVICE_PUSH_NON_FF_MATCHING]			= { "pushNonFFMatching" },
+	[ADVICE_PUSH_REF_NEEDS_UPDATE]			= { "pushRefNeedsUpdate" },
+	[ADVICE_PUSH_UNQUALIFIED_REF_NAME]		= { "pushUnqualifiedRefName" },
+	[ADVICE_PUSH_UPDATE_REJECTED]			= { "pushUpdateRejected" },
+	[ADVICE_PUSH_UPDATE_REJECTED_ALIAS]		= { "pushNonFastForward" }, /* backwards compatibility */
+	[ADVICE_RESET_NO_REFRESH_WARNING]		= { "resetNoRefresh" },
+	[ADVICE_RESOLVE_CONFLICT]			= { "resolveConflict" },
+	[ADVICE_RM_HINTS]				= { "rmHints" },
+	[ADVICE_SEQUENCER_IN_USE]			= { "sequencerInUse" },
+	[ADVICE_SET_UPSTREAM_FAILURE]			= { "setUpstreamFailure" },
+	[ADVICE_SKIPPED_CHERRY_PICKS]			= { "skippedCherryPicks" },
+	[ADVICE_STATUS_AHEAD_BEHIND_WARNING]		= { "statusAheadBehindWarning" },
+	[ADVICE_STATUS_HINTS]				= { "statusHints" },
+	[ADVICE_STATUS_U_OPTION]			= { "statusUoption" },
+	[ADVICE_SUBMODULES_NOT_UPDATED] 		= { "submodulesNotUpdated" },
+	[ADVICE_SUBMODULE_ALTERNATE_ERROR_STRATEGY_DIE] = { "submoduleAlternateErrorStrategyDie" },
+	[ADVICE_SUGGEST_DETACHING_HEAD]			= { "suggestDetachingHead" },
+	[ADVICE_UPDATE_SPARSE_PATH]			= { "updateSparsePath" },
+	[ADVICE_WAITING_FOR_EDITOR]			= { "waitingForEditor" },
+	[ADVICE_WORKTREE_ADD_ORPHAN]			= { "worktreeAddOrphan" },
 };
 
 static const char turn_off_instructions[] =
@@ -118,13 +122,13 @@ void advise(const char *advice, ...)
 
 int advice_enabled(enum advice_type type)
 {
-	switch(type) {
-	case ADVICE_PUSH_UPDATE_REJECTED:
-		return advice_setting[ADVICE_PUSH_UPDATE_REJECTED].enabled &&
-		       advice_setting[ADVICE_PUSH_UPDATE_REJECTED_ALIAS].enabled;
-	default:
-		return advice_setting[type].enabled;
-	}
+	int enabled = advice_setting[type].level != ADVICE_LEVEL_DISABLED;
+
+	if (type == ADVICE_PUSH_UPDATE_REJECTED)
+		return enabled &&
+		       advice_enabled(ADVICE_PUSH_UPDATE_REJECTED_ALIAS);
+
+	return enabled;
 }
 
 void advise_if_enabled(enum advice_type type, const char *advice, ...)
@@ -135,7 +139,8 @@ void advise_if_enabled(enum advice_type type, const char *advice, ...)
 		return;
 
 	va_start(params, advice);
-	vadvise(advice, 1, advice_setting[type].key, params);
+	vadvise(advice, !advice_setting[type].level, advice_setting[type].key,
+		params);
 	va_end(params);
 }
 
@@ -164,7 +169,9 @@ int git_default_advice_config(const char *var, const char *value)
 	for (i = 0; i < ARRAY_SIZE(advice_setting); i++) {
 		if (strcasecmp(k, advice_setting[i].key))
 			continue;
-		advice_setting[i].enabled = git_config_bool(var, value);
+		advice_setting[i].level = git_config_bool(var, value)
+					  ? ADVICE_LEVEL_ENABLED
+					  : ADVICE_LEVEL_DISABLED;
 		return 0;
 	}
 
diff --git a/advice.h b/advice.h
index 2affbe1..9d4f49a 100644
--- a/advice.h
+++ b/advice.h
@@ -10,18 +10,18 @@ struct string_list;
  * Add the new config variable to Documentation/config/advice.txt.
  * Call advise_if_enabled to print your advice.
  */
- enum advice_type {
+enum advice_type {
 	ADVICE_ADD_EMBEDDED_REPO,
 	ADVICE_ADD_EMPTY_PATHSPEC,
 	ADVICE_ADD_IGNORED_FILE,
-	ADVICE_AM_WORK_DIR,
 	ADVICE_AMBIGUOUS_FETCH_REFSPEC,
+	ADVICE_AM_WORK_DIR,
 	ADVICE_CHECKOUT_AMBIGUOUS_REMOTE_BRANCH_NAME,
 	ADVICE_COMMIT_BEFORE_MERGE,
 	ADVICE_DETACHED_HEAD,
 	ADVICE_DIVERGING,
-	ADVICE_SUGGEST_DETACHING_HEAD,
 	ADVICE_FETCH_SHOW_FORCED_UPDATES,
+	ADVICE_FORCE_DELETE_BRANCH,
 	ADVICE_GRAFT_FILE_DEPRECATED,
 	ADVICE_IGNORED_HOOK,
 	ADVICE_IMPLICIT_IDENTITY,
@@ -32,23 +32,24 @@ struct string_list;
 	ADVICE_PUSH_NEEDS_FORCE,
 	ADVICE_PUSH_NON_FF_CURRENT,
 	ADVICE_PUSH_NON_FF_MATCHING,
-	ADVICE_PUSH_UNQUALIFIED_REF_NAME,
-	ADVICE_PUSH_UPDATE_REJECTED_ALIAS,
-	ADVICE_PUSH_UPDATE_REJECTED,
 	ADVICE_PUSH_REF_NEEDS_UPDATE,
+	ADVICE_PUSH_UNQUALIFIED_REF_NAME,
+	ADVICE_PUSH_UPDATE_REJECTED,
+	ADVICE_PUSH_UPDATE_REJECTED_ALIAS,
 	ADVICE_RESET_NO_REFRESH_WARNING,
 	ADVICE_RESOLVE_CONFLICT,
 	ADVICE_RM_HINTS,
 	ADVICE_SEQUENCER_IN_USE,
 	ADVICE_SET_UPSTREAM_FAILURE,
+	ADVICE_SKIPPED_CHERRY_PICKS,
 	ADVICE_STATUS_AHEAD_BEHIND_WARNING,
 	ADVICE_STATUS_HINTS,
 	ADVICE_STATUS_U_OPTION,
-	ADVICE_SUBMODULE_ALTERNATE_ERROR_STRATEGY_DIE,
 	ADVICE_SUBMODULES_NOT_UPDATED,
+	ADVICE_SUBMODULE_ALTERNATE_ERROR_STRATEGY_DIE,
+	ADVICE_SUGGEST_DETACHING_HEAD,
 	ADVICE_UPDATE_SPARSE_PATH,
 	ADVICE_WAITING_FOR_EDITOR,
-	ADVICE_SKIPPED_CHERRY_PICKS,
 	ADVICE_WORKTREE_ADD_ORPHAN,
 };
 
diff --git a/attr.c b/attr.c
index e62876d..679e422 100644
--- a/attr.c
+++ b/attr.c
@@ -17,6 +17,7 @@
 #include "utf8.h"
 #include "quote.h"
 #include "read-cache-ll.h"
+#include "refs.h"
 #include "revision.h"
 #include "object-store-ll.h"
 #include "setup.h"
@@ -183,6 +184,15 @@ static void all_attrs_init(struct attr_hashmap *map, struct attr_check *check)
 	}
 }
 
+/*
+ * Atribute name cannot begin with "builtin_" which
+ * is a reserved namespace for built in attributes values.
+ */
+static int attr_name_reserved(const char *name)
+{
+	return starts_with(name, "builtin_");
+}
+
 static int attr_name_valid(const char *name, size_t namelen)
 {
 	/*
@@ -315,7 +325,7 @@ static const char *parse_attr(const char *src, int lineno, const char *cp,
 			cp++;
 			len--;
 		}
-		if (!attr_name_valid(cp, len)) {
+		if (!attr_name_valid(cp, len) || attr_name_reserved(cp)) {
 			report_invalid_attr(cp, len, src, lineno);
 			return NULL;
 		}
@@ -379,7 +389,7 @@ static struct match_attr *parse_attr_line(const char *line, const char *src,
 		name += strlen(ATTRIBUTE_MACRO_PREFIX);
 		name += strspn(name, blank);
 		namelen = strcspn(name, blank);
-		if (!attr_name_valid(name, namelen)) {
+		if (!attr_name_valid(name, namelen) || attr_name_reserved(name)) {
 			report_invalid_attr(name, namelen, src, lineno);
 			goto fail_return;
 		}
@@ -1240,6 +1250,85 @@ static struct object_id *default_attr_source(void)
 	return &attr_source;
 }
 
+static const char *interned_mode_string(unsigned int mode)
+{
+	static struct {
+		unsigned int val;
+		char str[7];
+	} mode_string[] = {
+		{ .val = 0040000 },
+		{ .val = 0100644 },
+		{ .val = 0100755 },
+		{ .val = 0120000 },
+		{ .val = 0160000 },
+	};
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(mode_string); i++) {
+		if (mode_string[i].val != mode)
+			continue;
+		if (!*mode_string[i].str)
+			snprintf(mode_string[i].str, sizeof(mode_string[i].str),
+				 "%06o", mode);
+		return mode_string[i].str;
+	}
+	BUG("Unsupported mode 0%o", mode);
+}
+
+static const char *builtin_object_mode_attr(struct index_state *istate, const char *path)
+{
+	unsigned int mode;
+
+	if (direction == GIT_ATTR_CHECKIN) {
+		struct object_id oid;
+		struct stat st;
+		if (lstat(path, &st))
+			die_errno(_("unable to stat '%s'"), path);
+		mode = canon_mode(st.st_mode);
+		if (S_ISDIR(mode)) {
+			/*
+			 *`path` is either a directory or it is a submodule,
+			 * in which case it is already indexed as submodule
+			 * or it does not exist in the index yet and we need to
+			 * check if we can resolve to a ref.
+			*/
+			int pos = index_name_pos(istate, path, strlen(path));
+			if (pos >= 0) {
+				 if (S_ISGITLINK(istate->cache[pos]->ce_mode))
+					 mode = istate->cache[pos]->ce_mode;
+			} else if (resolve_gitlink_ref(path, "HEAD", &oid) == 0) {
+				mode = S_IFGITLINK;
+			}
+		}
+	} else {
+		/*
+		 * For GIT_ATTR_CHECKOUT and GIT_ATTR_INDEX we only check
+		 * for mode in the index.
+		 */
+		int pos = index_name_pos(istate, path, strlen(path));
+		if (pos >= 0)
+			mode = istate->cache[pos]->ce_mode;
+		else
+			return ATTR__UNSET;
+	}
+
+	return interned_mode_string(mode);
+}
+
+
+static const char *compute_builtin_attr(struct index_state *istate,
+					  const char *path,
+					  const struct git_attr *attr) {
+	static const struct git_attr *object_mode_attr;
+
+	if (!object_mode_attr)
+		object_mode_attr = git_attr("builtin_objectmode");
+
+	if (attr == object_mode_attr)
+		return builtin_object_mode_attr(istate, path);
+	return ATTR__UNSET;
+}
+
 void git_check_attr(struct index_state *istate,
 		    const char *path,
 		    struct attr_check *check)
@@ -1253,7 +1342,7 @@ void git_check_attr(struct index_state *istate,
 		unsigned int n = check->items[i].attr->attr_nr;
 		const char *value = check->all_attrs[n].value;
 		if (value == ATTR__UNKNOWN)
-			value = ATTR__UNSET;
+			value = compute_builtin_attr(istate, path, check->all_attrs[n].attr);
 		check->items[i].value = value;
 	}
 }
diff --git a/bisect.c b/bisect.c
index 8487f8c..f1273c7 100644
--- a/bisect.c
+++ b/bisect.c
@@ -470,7 +470,6 @@ static int read_bisect_refs(void)
 }
 
 static GIT_PATH_FUNC(git_path_bisect_names, "BISECT_NAMES")
-static GIT_PATH_FUNC(git_path_bisect_expected_rev, "BISECT_EXPECTED_REV")
 static GIT_PATH_FUNC(git_path_bisect_ancestors_ok, "BISECT_ANCESTORS_OK")
 static GIT_PATH_FUNC(git_path_bisect_run, "BISECT_RUN")
 static GIT_PATH_FUNC(git_path_bisect_start, "BISECT_START")
@@ -706,26 +705,10 @@ static enum bisect_error error_if_skipped_commits(struct commit_list *tried,
 
 static int is_expected_rev(const struct object_id *oid)
 {
-	const char *filename = git_path_bisect_expected_rev();
-	struct stat st;
-	struct strbuf str = STRBUF_INIT;
-	FILE *fp;
-	int res = 0;
-
-	if (stat(filename, &st) || !S_ISREG(st.st_mode))
+	struct object_id expected_oid;
+	if (read_ref("BISECT_EXPECTED_REV", &expected_oid))
 		return 0;
-
-	fp = fopen_or_warn(filename, "r");
-	if (!fp)
-		return 0;
-
-	if (strbuf_getline_lf(&str, fp) != EOF)
-		res = !strcmp(str.buf, oid_to_hex(oid));
-
-	strbuf_release(&str);
-	fclose(fp);
-
-	return res;
+	return oideq(oid, &expected_oid);
 }
 
 enum bisect_error bisect_checkout(const struct object_id *bisect_rev,
@@ -1184,10 +1167,10 @@ int bisect_clean_state(void)
 	struct string_list refs_for_removal = STRING_LIST_INIT_NODUP;
 	for_each_ref_in("refs/bisect", mark_for_removal, (void *) &refs_for_removal);
 	string_list_append(&refs_for_removal, xstrdup("BISECT_HEAD"));
+	string_list_append(&refs_for_removal, xstrdup("BISECT_EXPECTED_REV"));
 	result = delete_refs("bisect: remove", &refs_for_removal, REF_NO_DEREF);
 	refs_for_removal.strdup_strings = 1;
 	string_list_clear(&refs_for_removal, 0);
-	unlink_or_warn(git_path_bisect_expected_rev());
 	unlink_or_warn(git_path_bisect_ancestors_ok());
 	unlink_or_warn(git_path_bisect_log());
 	unlink_or_warn(git_path_bisect_names());
diff --git a/branch.c b/branch.c
index 534594f..6719a18 100644
--- a/branch.c
+++ b/branch.c
@@ -817,8 +817,9 @@ void remove_merge_branch_state(struct repository *r)
 	unlink(git_path_merge_rr(r));
 	unlink(git_path_merge_msg(r));
 	unlink(git_path_merge_mode(r));
-	unlink(git_path_auto_merge(r));
-	save_autostash(git_path_merge_autostash(r));
+	refs_delete_ref(get_main_ref_store(r), "", "AUTO_MERGE",
+			NULL, REF_NO_DEREF);
+	save_autostash_ref(r, "MERGE_AUTOSTASH");
 }
 
 void remove_branch_state(struct repository *r, int verbose)
diff --git a/builtin.h b/builtin.h
index d560baa..2828063 100644
--- a/builtin.h
+++ b/builtin.h
@@ -211,6 +211,7 @@ int cmd_remote(int argc, const char **argv, const char *prefix);
 int cmd_remote_ext(int argc, const char **argv, const char *prefix);
 int cmd_remote_fd(int argc, const char **argv, const char *prefix);
 int cmd_repack(int argc, const char **argv, const char *prefix);
+int cmd_replay(int argc, const char **argv, const char *prefix);
 int cmd_rerere(int argc, const char **argv, const char *prefix);
 int cmd_reset(int argc, const char **argv, const char *prefix);
 int cmd_restore(int argc, const char **argv, const char *prefix);
diff --git a/builtin/add.c b/builtin/add.c
index 2151c45..ada7719 100644
--- a/builtin/add.c
+++ b/builtin/add.c
@@ -421,7 +421,7 @@ int cmd_add(int argc, const char **argv, const char *prefix)
 	 * Check the "pathspec '%s' did not match any files" block
 	 * below before enabling new magic.
 	 */
-	parse_pathspec(&pathspec, PATHSPEC_ATTR,
+	parse_pathspec(&pathspec, 0,
 		       PATHSPEC_PREFER_FULL |
 		       PATHSPEC_SYMLINK_LEADING_PATH,
 		       prefix, argv);
@@ -430,7 +430,7 @@ int cmd_add(int argc, const char **argv, const char *prefix)
 		if (pathspec.nr)
 			die(_("'%s' and pathspec arguments cannot be used together"), "--pathspec-from-file");
 
-		parse_pathspec_file(&pathspec, PATHSPEC_ATTR,
+		parse_pathspec_file(&pathspec, 0,
 				    PATHSPEC_PREFER_FULL |
 				    PATHSPEC_SYMLINK_LEADING_PATH,
 				    prefix, pathspec_from_file, pathspec_file_nul);
@@ -501,7 +501,8 @@ int cmd_add(int argc, const char **argv, const char *prefix)
 			       PATHSPEC_LITERAL |
 			       PATHSPEC_GLOB |
 			       PATHSPEC_ICASE |
-			       PATHSPEC_EXCLUDE);
+			       PATHSPEC_EXCLUDE |
+			       PATHSPEC_ATTR);
 
 		for (i = 0; i < pathspec.nr; i++) {
 			const char *path = pathspec.items[i].match;
diff --git a/builtin/bisect.c b/builtin/bisect.c
index 032beaa..f69c3f7 100644
--- a/builtin/bisect.c
+++ b/builtin/bisect.c
@@ -16,7 +16,6 @@
 #include "revision.h"
 
 static GIT_PATH_FUNC(git_path_bisect_terms, "BISECT_TERMS")
-static GIT_PATH_FUNC(git_path_bisect_expected_rev, "BISECT_EXPECTED_REV")
 static GIT_PATH_FUNC(git_path_bisect_ancestors_ok, "BISECT_ANCESTORS_OK")
 static GIT_PATH_FUNC(git_path_bisect_start, "BISECT_START")
 static GIT_PATH_FUNC(git_path_bisect_log, "BISECT_LOG")
@@ -919,7 +918,6 @@ static enum bisect_error bisect_state(struct bisect_terms *terms, int argc,
 	const char *state;
 	int i, verify_expected = 1;
 	struct object_id oid, expected;
-	struct strbuf buf = STRBUF_INIT;
 	struct oid_array revs = OID_ARRAY_INIT;
 
 	if (!argc)
@@ -974,10 +972,8 @@ static enum bisect_error bisect_state(struct bisect_terms *terms, int argc,
 		oid_array_append(&revs, &commit->object.oid);
 	}
 
-	if (strbuf_read_file(&buf, git_path_bisect_expected_rev(), 0) < the_hash_algo->hexsz ||
-	    get_oid_hex(buf.buf, &expected) < 0)
+	if (read_ref("BISECT_EXPECTED_REV", &expected))
 		verify_expected = 0; /* Ignore invalid file contents */
-	strbuf_release(&buf);
 
 	for (i = 0; i < revs.nr; i++) {
 		if (bisect_write(state, oid_to_hex(&revs.oid[i]), terms, 0)) {
@@ -986,7 +982,7 @@ static enum bisect_error bisect_state(struct bisect_terms *terms, int argc,
 		}
 		if (verify_expected && !oideq(&revs.oid[i], &expected)) {
 			unlink_or_warn(git_path_bisect_ancestors_ok());
-			unlink_or_warn(git_path_bisect_expected_rev());
+			delete_ref(NULL, "BISECT_EXPECTED_REV", NULL, REF_NO_DEREF);
 			verify_expected = 0;
 		}
 	}
diff --git a/builtin/branch.c b/builtin/branch.c
index 6e30d5e..cfb63cc 100644
--- a/builtin/branch.c
+++ b/builtin/branch.c
@@ -24,6 +24,7 @@
 #include "ref-filter.h"
 #include "worktree.h"
 #include "help.h"
+#include "advice.h"
 #include "commit-reach.h"
 
 static const char * const builtin_branch_usage[] = {
@@ -42,7 +43,6 @@ static const char *head;
 static struct object_id head_oid;
 static int recurse_submodules = 0;
 static int submodule_propagate_branches = 0;
-static int omit_empty = 0;
 
 static int branch_use_color = -1;
 static char branch_colors[][COLOR_MAXLEN] = {
@@ -191,9 +191,10 @@ static int check_branch_commit(const char *branchname, const char *refname,
 		return -1;
 	}
 	if (!force && !branch_merged(kinds, branchname, rev, head_rev)) {
-		error(_("the branch '%s' is not fully merged.\n"
-		      "If you are sure you want to delete it, "
-		      "run 'git branch -D %s'"), branchname, branchname);
+		error(_("the branch '%s' is not fully merged"), branchname);
+		advise_if_enabled(ADVICE_FORCE_DELETE_BRANCH,
+				  _("If you are sure you want to delete it, "
+				  "run 'git branch -D %s'"), branchname);
 		return -1;
 	}
 	return 0;
@@ -435,8 +436,6 @@ static void print_ref_list(struct ref_filter *filter, struct ref_sorting *sortin
 {
 	int i;
 	struct ref_array array;
-	struct strbuf out = STRBUF_INIT;
-	struct strbuf err = STRBUF_INIT;
 	int maxwidth = 0;
 	const char *remote_prefix = "";
 	char *to_free = NULL;
@@ -466,24 +465,27 @@ static void print_ref_list(struct ref_filter *filter, struct ref_sorting *sortin
 	filter_ahead_behind(the_repository, format, &array);
 	ref_array_sort(sorting, &array);
 
-	for (i = 0; i < array.nr; i++) {
-		strbuf_reset(&err);
-		strbuf_reset(&out);
-		if (format_ref_array_item(array.items[i], format, &out, &err))
-			die("%s", err.buf);
-		if (column_active(colopts)) {
-			assert(!filter->verbose && "--column and --verbose are incompatible");
-			 /* format to a string_list to let print_columns() do its job */
+	if (column_active(colopts)) {
+		struct strbuf out = STRBUF_INIT, err = STRBUF_INIT;
+
+		assert(!filter->verbose && "--column and --verbose are incompatible");
+
+		for (i = 0; i < array.nr; i++) {
+			strbuf_reset(&err);
+			strbuf_reset(&out);
+			if (format_ref_array_item(array.items[i], format, &out, &err))
+				die("%s", err.buf);
+
+			/* format to a string_list to let print_columns() do its job */
 			string_list_append(output, out.buf);
-		} else {
-			fwrite(out.buf, 1, out.len, stdout);
-			if (out.len || !omit_empty)
-				putchar('\n');
 		}
+
+		strbuf_release(&err);
+		strbuf_release(&out);
+	} else {
+		print_formatted_ref_array(&array, format);
 	}
 
-	strbuf_release(&err);
-	strbuf_release(&out);
 	ref_array_clear(&array);
 	free(to_free);
 }
@@ -734,7 +736,7 @@ int cmd_branch(int argc, const char **argv, const char *prefix)
 		OPT_BIT('D', NULL, &delete, N_("delete branch (even if not merged)"), 2),
 		OPT_BIT('m', "move", &rename, N_("move/rename a branch and its reflog"), 1),
 		OPT_BIT('M', NULL, &rename, N_("move/rename a branch, even if target exists"), 2),
-		OPT_BOOL(0, "omit-empty",  &omit_empty,
+		OPT_BOOL(0, "omit-empty",  &format.array_opts.omit_empty,
 			N_("do not output a newline after empty formatted refs")),
 		OPT_BIT('c', "copy", &copy, N_("copy a branch and its reflog"), 1),
 		OPT_BIT('C', NULL, &copy, N_("copy a branch, even if target exists"), 2),
@@ -764,7 +766,13 @@ int cmd_branch(int argc, const char **argv, const char *prefix)
 	if (argc == 2 && !strcmp(argv[1], "-h"))
 		usage_with_options(builtin_branch_usage, options);
 
+	/*
+	 * Try to set sort keys from config. If config does not set any,
+	 * fall back on default (refname) sorting.
+	 */
 	git_config(git_branch_config, &sorting_options);
+	if (!sorting_options.nr)
+		string_list_append(&sorting_options, "refname");
 
 	track = git_branch_track;
 
diff --git a/builtin/checkout.c b/builtin/checkout.c
index 3a7bfde..a6e3093 100644
--- a/builtin/checkout.c
+++ b/builtin/checkout.c
@@ -1515,6 +1515,26 @@ static void die_if_some_operation_in_progress(void)
 	wt_status_state_free_buffers(&state);
 }
 
+/*
+ * die if attempting to checkout an existing branch that is in use
+ * in another worktree, unless ignore-other-wortrees option is given.
+ * The check is bypassed when the branch is already the current one,
+ * as it will not make things any worse.
+ */
+static void die_if_switching_to_a_branch_in_use(struct checkout_opts *opts,
+						const char *full_ref)
+{
+	int flags;
+	char *head_ref;
+
+	if (opts->ignore_other_worktrees)
+		return;
+	head_ref = resolve_refdup("HEAD", 0, NULL, &flags);
+	if (head_ref && (!(flags & REF_ISSYMREF) || strcmp(head_ref, full_ref)))
+		die_if_checked_out(full_ref, 1);
+	free(head_ref);
+}
+
 static int checkout_branch(struct checkout_opts *opts,
 			   struct branch_info *new_branch_info)
 {
@@ -1575,14 +1595,15 @@ static int checkout_branch(struct checkout_opts *opts,
 	if (!opts->can_switch_when_in_progress)
 		die_if_some_operation_in_progress();
 
-	if (new_branch_info->path && !opts->force_detach && !opts->new_branch &&
-	    !opts->ignore_other_worktrees) {
-		int flag;
-		char *head_ref = resolve_refdup("HEAD", 0, NULL, &flag);
-		if (head_ref &&
-		    (!(flag & REF_ISSYMREF) || strcmp(head_ref, new_branch_info->path)))
-			die_if_checked_out(new_branch_info->path, 1);
-		free(head_ref);
+	/* "git checkout <branch>" */
+	if (new_branch_info->path && !opts->force_detach && !opts->new_branch)
+		die_if_switching_to_a_branch_in_use(opts, new_branch_info->path);
+
+	/* "git checkout -B <branch>" */
+	if (opts->new_branch_force) {
+		char *full_ref = xstrfmt("refs/heads/%s", opts->new_branch);
+		die_if_switching_to_a_branch_in_use(opts, full_ref);
+		free(full_ref);
 	}
 
 	if (!new_branch_info->commit && opts->new_branch) {
diff --git a/builtin/clone.c b/builtin/clone.c
index 315befa..bad1b70 100644
--- a/builtin/clone.c
+++ b/builtin/clone.c
@@ -71,6 +71,7 @@ static char *remote_name = NULL;
 static char *option_branch = NULL;
 static struct string_list option_not = STRING_LIST_INIT_NODUP;
 static const char *real_git_dir;
+static const char *ref_format;
 static char *option_upload_pack = "git-upload-pack";
 static int option_verbosity;
 static int option_progress = -1;
@@ -156,6 +157,8 @@ static struct option builtin_clone_options[] = {
 		    N_("any cloned submodules will be shallow")),
 	OPT_STRING(0, "separate-git-dir", &real_git_dir, N_("gitdir"),
 		   N_("separate git dir from working tree")),
+	OPT_STRING(0, "ref-format", &ref_format, N_("format"),
+		   N_("specify the reference format to use")),
 	OPT_STRING_LIST('c', "config", &option_config, N_("key=value"),
 			N_("set config inside the new repository")),
 	OPT_STRING_LIST(0, "server-option", &server_options,
@@ -931,6 +934,7 @@ int cmd_clone(int argc, const char **argv, const char *prefix)
 	int submodule_progress;
 	int filter_submodules = 0;
 	int hash_algo;
+	unsigned int ref_storage_format = REF_STORAGE_FORMAT_UNKNOWN;
 	const int do_not_override_repo_unix_permissions = -1;
 
 	struct transport_ls_refs_options transport_ls_refs_options =
@@ -956,6 +960,12 @@ int cmd_clone(int argc, const char **argv, const char *prefix)
 	if (option_single_branch == -1)
 		option_single_branch = deepen ? 1 : 0;
 
+	if (ref_format) {
+		ref_storage_format = ref_storage_format_by_name(ref_format);
+		if (ref_storage_format == REF_STORAGE_FORMAT_UNKNOWN)
+			die(_("unknown ref storage format '%s'"), ref_format);
+	}
+
 	if (option_mirror)
 		option_bare = 1;
 
@@ -1100,8 +1110,15 @@ int cmd_clone(int argc, const char **argv, const char *prefix)
 		}
 	}
 
-	init_db(git_dir, real_git_dir, option_template, GIT_HASH_UNKNOWN, NULL,
-		do_not_override_repo_unix_permissions, INIT_DB_QUIET);
+	/*
+	 * Initialize the repository, but skip initializing the reference
+	 * database. We do not yet know about the object format of the
+	 * repository, and reference backends may persist that information into
+	 * their on-disk data structures.
+	 */
+	init_db(git_dir, real_git_dir, option_template, GIT_HASH_UNKNOWN,
+		ref_storage_format, NULL,
+		do_not_override_repo_unix_permissions, INIT_DB_QUIET | INIT_DB_SKIP_REFDB);
 
 	if (real_git_dir) {
 		free((char *)git_dir);
@@ -1188,10 +1205,7 @@ int cmd_clone(int argc, const char **argv, const char *prefix)
 	if (option_required_reference.nr || option_optional_reference.nr)
 		setup_reference();
 
-	if (option_sparse_checkout && git_sparse_checkout_init(dir))
-		return 1;
-
-	remote = remote_get(remote_name);
+	remote = remote_get_early(remote_name);
 
 	refspec_appendf(&remote->fetch, "+%s*:%s*", src_ref_prefix,
 			branch_top.buf);
@@ -1269,6 +1283,27 @@ int cmd_clone(int argc, const char **argv, const char *prefix)
 	if (transport->smart_options && !deepen && !filter_options.choice)
 		transport->smart_options->check_self_contained_and_connected = 1;
 
+	strvec_push(&transport_ls_refs_options.ref_prefixes, "HEAD");
+	refspec_ref_prefixes(&remote->fetch,
+			     &transport_ls_refs_options.ref_prefixes);
+	if (option_branch)
+		expand_ref_prefix(&transport_ls_refs_options.ref_prefixes,
+				  option_branch);
+	if (!option_no_tags)
+		strvec_push(&transport_ls_refs_options.ref_prefixes,
+			    "refs/tags/");
+
+	refs = transport_get_remote_refs(transport, &transport_ls_refs_options);
+
+	/*
+	 * Now that we know what algorithm the remote side is using, let's set
+	 * ours to the same thing.
+	 */
+	hash_algo = hash_algo_by_ptr(transport_get_hash_algo(transport));
+	initialize_repository_version(hash_algo, the_repository->ref_storage_format, 1);
+	repo_set_hash_algo(the_repository, hash_algo);
+	create_reference_database(the_repository->ref_storage_format, NULL, 1);
+
 	/*
 	 * Before fetching from the remote, download and install bundle
 	 * data from the --bundle-uri option.
@@ -1284,24 +1319,7 @@ int cmd_clone(int argc, const char **argv, const char *prefix)
 				bundle_uri);
 		else if (has_heuristic)
 			git_config_set_gently("fetch.bundleuri", bundle_uri);
-	}
-
-	strvec_push(&transport_ls_refs_options.ref_prefixes, "HEAD");
-	refspec_ref_prefixes(&remote->fetch,
-			     &transport_ls_refs_options.ref_prefixes);
-	if (option_branch)
-		expand_ref_prefix(&transport_ls_refs_options.ref_prefixes,
-				  option_branch);
-	if (!option_no_tags)
-		strvec_push(&transport_ls_refs_options.ref_prefixes,
-			    "refs/tags/");
-
-	refs = transport_get_remote_refs(transport, &transport_ls_refs_options);
-
-	if (refs)
-		mapped_refs = wanted_peer_refs(refs, &remote->fetch);
-
-	if (!bundle_uri) {
+	} else {
 		/*
 		* Populate transport->got_remote_bundle_uri and
 		* transport->bundle_uri. We might get nothing.
@@ -1322,13 +1340,8 @@ int cmd_clone(int argc, const char **argv, const char *prefix)
 		}
 	}
 
-		/*
-		 * Now that we know what algorithm the remote side is using,
-		 * let's set ours to the same thing.
-		 */
-	hash_algo = hash_algo_by_ptr(transport_get_hash_algo(transport));
-	initialize_repository_version(hash_algo, 1);
-	repo_set_hash_algo(the_repository, hash_algo);
+	if (refs)
+		mapped_refs = wanted_peer_refs(refs, &remote->fetch);
 
 	if (mapped_refs) {
 		/*
@@ -1431,6 +1444,9 @@ int cmd_clone(int argc, const char **argv, const char *prefix)
 		dissociate_from_references();
 	}
 
+	if (option_sparse_checkout && git_sparse_checkout_init(dir))
+		return 1;
+
 	junk_mode = JUNK_LEAVE_REPO;
 	err = checkout(submodule_progress, filter_submodules);
 
diff --git a/builtin/commit-graph.c b/builtin/commit-graph.c
index 666ad57..7102ee9 100644
--- a/builtin/commit-graph.c
+++ b/builtin/commit-graph.c
@@ -21,7 +21,7 @@
 	N_("git commit-graph write [--object-dir <dir>] [--append]\n" \
 	   "                       [--split[=<strategy>]] [--reachable | --stdin-packs | --stdin-commits]\n" \
 	   "                       [--changed-paths] [--[no-]max-new-filters <n>] [--[no-]progress]\n" \
-	   "                       <split options>")
+	   "                       <split-options>")
 
 static const char * builtin_commit_graph_verify_usage[] = {
 	BUILTIN_COMMIT_GRAPH_VERIFY_USAGE,
diff --git a/builtin/commit.c b/builtin/commit.c
index 65196a2..6d1fa71 100644
--- a/builtin/commit.c
+++ b/builtin/commit.c
@@ -1877,7 +1877,7 @@ int cmd_commit(int argc, const char **argv, const char *prefix)
 				     &oid, flags);
 	}
 
-	apply_autostash(git_path_merge_autostash(the_repository));
+	apply_autostash_ref(the_repository, "MERGE_AUTOSTASH");
 
 cleanup:
 	strbuf_release(&author_ident);
diff --git a/builtin/config.c b/builtin/config.c
index 11a4d4e..b55bfae 100644
--- a/builtin/config.c
+++ b/builtin/config.c
@@ -708,10 +708,8 @@ int cmd_config(int argc, const char **argv, const char *prefix)
 	}
 
 	if (use_global_config) {
-		char *user_config, *xdg_config;
-
-		git_global_config(&user_config, &xdg_config);
-		if (!user_config)
+		given_config_source.file = git_global_config();
+		if (!given_config_source.file)
 			/*
 			 * It is unknown if HOME/.gitconfig exists, so
 			 * we do not know if we should write to XDG
@@ -719,19 +717,8 @@ int cmd_config(int argc, const char **argv, const char *prefix)
 			 * is set and points at a sane location.
 			 */
 			die(_("$HOME not set"));
-
 		given_config_source.scope = CONFIG_SCOPE_GLOBAL;
-
-		if (access_or_warn(user_config, R_OK, 0) &&
-		    xdg_config && !access_or_warn(xdg_config, R_OK, 0)) {
-			given_config_source.file = xdg_config;
-			free(user_config);
-		} else {
-			given_config_source.file = user_config;
-			free(xdg_config);
-		}
-	}
-	else if (use_system_config) {
+	} else if (use_system_config) {
 		given_config_source.file = git_system_config();
 		given_config_source.scope = CONFIG_SCOPE_SYSTEM;
 	} else if (use_local_config) {
@@ -760,7 +747,6 @@ int cmd_config(int argc, const char **argv, const char *prefix)
 		given_config_source.scope = CONFIG_SCOPE_COMMAND;
 	}
 
-
 	if (respect_includes_opt == -1)
 		config_options.respect_includes = !given_config_source.file;
 	else
diff --git a/builtin/fetch.c b/builtin/fetch.c
index 119f1a7..3aedfd1 100644
--- a/builtin/fetch.c
+++ b/builtin/fetch.c
@@ -100,6 +100,7 @@ static struct string_list negotiation_tip = STRING_LIST_INIT_NODUP;
 
 struct fetch_config {
 	enum display_format display_format;
+	int all;
 	int prune;
 	int prune_tags;
 	int show_forced_updates;
@@ -113,6 +114,11 @@ static int git_fetch_config(const char *k, const char *v,
 {
 	struct fetch_config *fetch_config = cb;
 
+	if (!strcmp(k, "fetch.all")) {
+		fetch_config->all = git_config_bool(k, v);
+		return 0;
+	}
+
 	if (!strcmp(k, "fetch.prune")) {
 		fetch_config->prune = git_config_bool(k, v);
 		return 0;
@@ -2130,7 +2136,7 @@ int cmd_fetch(int argc, const char **argv, const char *prefix)
 	const char *bundle_uri;
 	struct string_list list = STRING_LIST_INIT_DUP;
 	struct remote *remote = NULL;
-	int all = 0, multiple = 0;
+	int all = -1, multiple = 0;
 	int result = 0;
 	int prune_tags_ok = 1;
 	int enable_auto_gc = 1;
@@ -2335,11 +2341,20 @@ int cmd_fetch(int argc, const char **argv, const char *prefix)
 	    fetch_bundle_uri(the_repository, bundle_uri, NULL))
 		warning(_("failed to fetch bundles from '%s'"), bundle_uri);
 
+	if (all < 0) {
+		/*
+		 * no --[no-]all given;
+		 * only use config option if no remote was explicitly specified
+		 */
+		all = (!argc) ? config.all : 0;
+	}
+
 	if (all) {
 		if (argc == 1)
 			die(_("fetch --all does not take a repository argument"));
 		else if (argc > 1)
 			die(_("fetch --all does not make sense with refspecs"));
+
 		(void) for_each_remote(get_one_remote_for_fetch, &list);
 
 		/* do not do fetch_multiple() of one */
diff --git a/builtin/for-each-ref.c b/builtin/for-each-ref.c
index b5bc700..3885a9c 100644
--- a/builtin/for-each-ref.c
+++ b/builtin/for-each-ref.c
@@ -18,15 +18,11 @@ static char const * const for_each_ref_usage[] = {
 
 int cmd_for_each_ref(int argc, const char **argv, const char *prefix)
 {
-	int i;
 	struct ref_sorting *sorting;
 	struct string_list sorting_options = STRING_LIST_INIT_DUP;
-	int maxcount = 0, icase = 0, omit_empty = 0;
-	struct ref_array array;
+	int icase = 0;
 	struct ref_filter filter = REF_FILTER_INIT;
 	struct ref_format format = REF_FORMAT_INIT;
-	struct strbuf output = STRBUF_INIT;
-	struct strbuf err = STRBUF_INIT;
 	int from_stdin = 0;
 	struct strvec vec = STRVEC_INIT;
 
@@ -39,11 +35,11 @@ int cmd_for_each_ref(int argc, const char **argv, const char *prefix)
 			N_("quote placeholders suitably for python"), QUOTE_PYTHON),
 		OPT_BIT(0 , "tcl",  &format.quote_style,
 			N_("quote placeholders suitably for Tcl"), QUOTE_TCL),
-		OPT_BOOL(0, "omit-empty",  &omit_empty,
+		OPT_BOOL(0, "omit-empty",  &format.array_opts.omit_empty,
 			N_("do not output a newline after empty formatted refs")),
 
 		OPT_GROUP(""),
-		OPT_INTEGER( 0 , "count", &maxcount, N_("show only <n> matched refs")),
+		OPT_INTEGER( 0 , "count", &format.array_opts.max_count, N_("show only <n> matched refs")),
 		OPT_STRING(  0 , "format", &format.format, N_("format"), N_("format to use for the output")),
 		OPT__COLOR(&format.use_color, N_("respect format colors")),
 		OPT_REF_FILTER_EXCLUDE(&filter),
@@ -60,15 +56,16 @@ int cmd_for_each_ref(int argc, const char **argv, const char *prefix)
 		OPT_END(),
 	};
 
-	memset(&array, 0, sizeof(array));
-
 	format.format = "%(objectname) %(objecttype)\t%(refname)";
 
 	git_config(git_default_config, NULL);
 
+	/* Set default (refname) sorting */
+	string_list_append(&sorting_options, "refname");
+
 	parse_options(argc, argv, prefix, opts, for_each_ref_usage, 0);
-	if (maxcount < 0) {
-		error("invalid --count argument: `%d'", maxcount);
+	if (format.array_opts.max_count < 0) {
+		error("invalid --count argument: `%d'", format.array_opts.max_count);
 		usage_with_options(for_each_ref_usage, opts);
 	}
 	if (HAS_MULTI_BITS(format.quote_style)) {
@@ -100,26 +97,8 @@ int cmd_for_each_ref(int argc, const char **argv, const char *prefix)
 	}
 
 	filter.match_as_path = 1;
-	filter_refs(&array, &filter, FILTER_REFS_ALL);
-	filter_ahead_behind(the_repository, &format, &array);
+	filter_and_format_refs(&filter, FILTER_REFS_ALL, sorting, &format);
 
-	ref_array_sort(sorting, &array);
-
-	if (!maxcount || array.nr < maxcount)
-		maxcount = array.nr;
-	for (i = 0; i < maxcount; i++) {
-		strbuf_reset(&err);
-		strbuf_reset(&output);
-		if (format_ref_array_item(array.items[i], &format, &output, &err))
-			die("%s", err.buf);
-		fwrite(output.buf, 1, output.len, stdout);
-		if (output.len || !omit_empty)
-			putchar('\n');
-	}
-
-	strbuf_release(&err);
-	strbuf_release(&output);
-	ref_array_clear(&array);
 	ref_filter_clear(&filter);
 	ref_sorting_release(sorting);
 	strvec_clear(&vec);
diff --git a/builtin/gc.c b/builtin/gc.c
index 7c11d5e..cb80ced 100644
--- a/builtin/gc.c
+++ b/builtin/gc.c
@@ -1543,19 +1543,18 @@ static int maintenance_register(int argc, const char **argv, const char *prefix)
 
 	if (!found) {
 		int rc;
-		char *user_config = NULL, *xdg_config = NULL;
+		char *global_config_file = NULL;
 
 		if (!config_file) {
-			git_global_config(&user_config, &xdg_config);
-			config_file = user_config;
-			if (!user_config)
-				die(_("$HOME not set"));
+			global_config_file = git_global_config();
+			config_file = global_config_file;
 		}
+		if (!config_file)
+			die(_("$HOME not set"));
 		rc = git_config_set_multivar_in_file_gently(
 			config_file, "maintenance.repo", maintpath,
 			CONFIG_REGEX_NONE, 0);
-		free(user_config);
-		free(xdg_config);
+		free(global_config_file);
 
 		if (rc)
 			die(_("unable to add '%s' value of '%s'"),
@@ -1612,18 +1611,18 @@ static int maintenance_unregister(int argc, const char **argv, const char *prefi
 
 	if (found) {
 		int rc;
-		char *user_config = NULL, *xdg_config = NULL;
+		char *global_config_file = NULL;
+
 		if (!config_file) {
-			git_global_config(&user_config, &xdg_config);
-			config_file = user_config;
-			if (!user_config)
-				die(_("$HOME not set"));
+			global_config_file = git_global_config();
+			config_file = global_config_file;
 		}
+		if (!config_file)
+			die(_("$HOME not set"));
 		rc = git_config_set_multivar_in_file_gently(
 			config_file, key, NULL, maintpath,
 			CONFIG_FLAGS_MULTI_REPLACE | CONFIG_FLAGS_FIXED_VALUE);
-		free(user_config);
-		free(xdg_config);
+		free(global_config_file);
 
 		if (rc &&
 		    (!force || rc == CONFIG_NOTHING_SET))
diff --git a/builtin/index-pack.c b/builtin/index-pack.c
index 1ea87e0..a3a37bd 100644
--- a/builtin/index-pack.c
+++ b/builtin/index-pack.c
@@ -24,7 +24,7 @@
 #include "setup.h"
 
 static const char index_pack_usage[] =
-"git index-pack [-v] [-o <index-file>] [--keep | --keep=<msg>] [--[no-]rev-index] [--verify] [--strict] (<pack-file> | --stdin [--fix-thin] [<pack-file>])";
+"git index-pack [-v] [-o <index-file>] [--keep | --keep=<msg>] [--[no-]rev-index] [--verify] [--strict[=<msg-id>=<severity>...]] [--fsck-objects[=<msg-id>=<severity>...]] (<pack-file> | --stdin [--fix-thin] [<pack-file>])";
 
 struct object_entry {
 	struct pack_idx_entry idx;
@@ -1785,8 +1785,9 @@ int cmd_index_pack(int argc, const char **argv, const char *prefix)
 			} else if (!strcmp(arg, "--check-self-contained-and-connected")) {
 				strict = 1;
 				check_self_contained_and_connected = 1;
-			} else if (!strcmp(arg, "--fsck-objects")) {
+			} else if (skip_to_optional_arg(arg, "--fsck-objects", &arg)) {
 				do_fsck_object = 1;
+				fsck_set_msg_types(&fsck_options, arg);
 			} else if (!strcmp(arg, "--verify")) {
 				verify = 1;
 			} else if (!strcmp(arg, "--verify-stat")) {
diff --git a/builtin/init-db.c b/builtin/init-db.c
index b89814a..0170469 100644
--- a/builtin/init-db.c
+++ b/builtin/init-db.c
@@ -10,6 +10,8 @@
 #include "object-file.h"
 #include "parse-options.h"
 #include "path.h"
+#include "refs.h"
+#include "repository.h"
 #include "setup.h"
 #include "strbuf.h"
 
@@ -56,6 +58,7 @@ static int shared_callback(const struct option *opt, const char *arg, int unset)
 static const char *const init_db_usage[] = {
 	N_("git init [-q | --quiet] [--bare] [--template=<template-directory>]\n"
 	   "         [--separate-git-dir <git-dir>] [--object-format=<format>]\n"
+	   "         [--ref-format=<format>]\n"
 	   "         [-b <branch-name> | --initial-branch=<branch-name>]\n"
 	   "         [--shared[=<permissions>]] [<directory>]"),
 	NULL
@@ -75,8 +78,10 @@ int cmd_init_db(int argc, const char **argv, const char *prefix)
 	const char *template_dir = NULL;
 	unsigned int flags = 0;
 	const char *object_format = NULL;
+	const char *ref_format = NULL;
 	const char *initial_branch = NULL;
 	int hash_algo = GIT_HASH_UNKNOWN;
+	unsigned int ref_storage_format = REF_STORAGE_FORMAT_UNKNOWN;
 	int init_shared_repository = -1;
 	const struct option init_db_options[] = {
 		OPT_STRING(0, "template", &template_dir, N_("template-directory"),
@@ -94,6 +99,8 @@ int cmd_init_db(int argc, const char **argv, const char *prefix)
 			   N_("override the name of the initial branch")),
 		OPT_STRING(0, "object-format", &object_format, N_("hash"),
 			   N_("specify the hash algorithm to use")),
+		OPT_STRING(0, "ref-format", &ref_format, N_("format"),
+			   N_("specify the reference format to use")),
 		OPT_END()
 	};
 
@@ -157,6 +164,12 @@ int cmd_init_db(int argc, const char **argv, const char *prefix)
 			die(_("unknown hash algorithm '%s'"), object_format);
 	}
 
+	if (ref_format) {
+		ref_storage_format = ref_storage_format_by_name(ref_format);
+		if (ref_storage_format == REF_STORAGE_FORMAT_UNKNOWN)
+			die(_("unknown ref storage format '%s'"), ref_format);
+	}
+
 	if (init_shared_repository != -1)
 		set_shared_repository(init_shared_repository);
 
@@ -235,5 +248,6 @@ int cmd_init_db(int argc, const char **argv, const char *prefix)
 
 	flags |= INIT_DB_EXIST_OK;
 	return init_db(git_dir, real_git_dir, template_dir, hash_algo,
-		       initial_branch, init_shared_repository, flags);
+		       ref_storage_format, initial_branch,
+		       init_shared_repository, flags);
 }
diff --git a/builtin/log.c b/builtin/log.c
index af6403c..db1808d 100644
--- a/builtin/log.c
+++ b/builtin/log.c
@@ -1365,6 +1365,7 @@ static void make_cover_letter(struct rev_info *rev, int use_separate_file,
 	pp.date_mode.type = DATE_RFC2822;
 	pp.rev = rev;
 	pp.print_email_subject = 1;
+	pp.encode_email_headers = rev->encode_email_headers;
 	pp_user_info(&pp, NULL, &sb, committer, encoding);
 	prepare_cover_text(&pp, description_file, branch_name, &sb,
 			   encoding, need_8bit_cte);
diff --git a/builtin/ls-remote.c b/builtin/ls-remote.c
index 2975ea4..e8d65eb 100644
--- a/builtin/ls-remote.c
+++ b/builtin/ls-remote.c
@@ -57,6 +57,7 @@ int cmd_ls_remote(int argc, const char **argv, const char *prefix)
 	struct transport *transport;
 	const struct ref *ref;
 	struct ref_array ref_array;
+	struct ref_sorting *sorting;
 	struct string_list sorting_options = STRING_LIST_INIT_DUP;
 
 	struct option options[] = {
@@ -140,13 +141,8 @@ int cmd_ls_remote(int argc, const char **argv, const char *prefix)
 		item->symref = xstrdup_or_null(ref->symref);
 	}
 
-	if (sorting_options.nr) {
-		struct ref_sorting *sorting;
-
-		sorting = ref_sorting_options(&sorting_options);
-		ref_array_sort(sorting, &ref_array);
-		ref_sorting_release(sorting);
-	}
+	sorting = ref_sorting_options(&sorting_options);
+	ref_array_sort(sorting, &ref_array);
 
 	for (i = 0; i < ref_array.nr; i++) {
 		const struct ref_array_item *ref = ref_array.items[i];
@@ -156,6 +152,7 @@ int cmd_ls_remote(int argc, const char **argv, const char *prefix)
 		status = 0; /* we found something */
 	}
 
+	ref_sorting_release(sorting);
 	ref_array_clear(&ref_array);
 	if (transport_disconnect(transport))
 		status = 1;
diff --git a/builtin/merge-file.c b/builtin/merge-file.c
index 832c93d..1f98733 100644
--- a/builtin/merge-file.c
+++ b/builtin/merge-file.c
@@ -1,5 +1,6 @@
 #include "builtin.h"
 #include "abspath.h"
+#include "diff.h"
 #include "hex.h"
 #include "object-name.h"
 #include "object-store.h"
@@ -28,6 +29,30 @@ static int label_cb(const struct option *opt, const char *arg, int unset)
 	return 0;
 }
 
+static int set_diff_algorithm(xpparam_t *xpp,
+			      const char *alg)
+{
+	long diff_algorithm = parse_algorithm_value(alg);
+	if (diff_algorithm < 0)
+		return -1;
+	xpp->flags = (xpp->flags & ~XDF_DIFF_ALGORITHM_MASK) | diff_algorithm;
+	return 0;
+}
+
+static int diff_algorithm_cb(const struct option *opt,
+				const char *arg, int unset)
+{
+	xpparam_t *xpp = opt->value;
+
+	BUG_ON_OPT_NEG(unset);
+
+	if (set_diff_algorithm(xpp, arg))
+		return error(_("option diff-algorithm accepts \"myers\", "
+			       "\"minimal\", \"patience\" and \"histogram\""));
+
+	return 0;
+}
+
 int cmd_merge_file(int argc, const char **argv, const char *prefix)
 {
 	const char *names[3] = { 0 };
@@ -48,6 +73,9 @@ int cmd_merge_file(int argc, const char **argv, const char *prefix)
 			    XDL_MERGE_FAVOR_THEIRS),
 		OPT_SET_INT(0, "union", &xmp.favor, N_("for conflicts, use a union version"),
 			    XDL_MERGE_FAVOR_UNION),
+		OPT_CALLBACK_F(0, "diff-algorithm", &xmp.xpp, N_("<algorithm>"),
+			     N_("choose a diff algorithm"),
+			     PARSE_OPT_NONEG, diff_algorithm_cb),
 		OPT_INTEGER(0, "marker-size", &xmp.marker_size,
 			    N_("for conflicts, use this marker size")),
 		OPT__QUIET(&quiet, N_("do not warn about conflicts")),
diff --git a/builtin/merge.c b/builtin/merge.c
index ebbe050..8f81978 100644
--- a/builtin/merge.c
+++ b/builtin/merge.c
@@ -476,7 +476,7 @@ static void finish(struct commit *head_commit,
 	run_hooks_l("post-merge", squash ? "1" : "0", NULL);
 
 	if (new_head)
-		apply_autostash(git_path_merge_autostash(the_repository));
+		apply_autostash_ref(the_repository, "MERGE_AUTOSTASH");
 	strbuf_release(&reflog_message);
 }
 
@@ -1315,7 +1315,8 @@ int cmd_merge(int argc, const char **argv, const char *prefix)
 	if (abort_current_merge) {
 		int nargc = 2;
 		const char *nargv[] = {"reset", "--merge", NULL};
-		struct strbuf stash_oid = STRBUF_INIT;
+		char stash_oid_hex[GIT_MAX_HEXSZ + 1];
+		struct object_id stash_oid = {0};
 
 		if (orig_argc != 2)
 			usage_msg_opt(_("--abort expects no arguments"),
@@ -1324,17 +1325,17 @@ int cmd_merge(int argc, const char **argv, const char *prefix)
 		if (!file_exists(git_path_merge_head(the_repository)))
 			die(_("There is no merge to abort (MERGE_HEAD missing)."));
 
-		if (read_oneliner(&stash_oid, git_path_merge_autostash(the_repository),
-		    READ_ONELINER_SKIP_IF_EMPTY))
-			unlink(git_path_merge_autostash(the_repository));
+		if (!read_ref("MERGE_AUTOSTASH", &stash_oid))
+			delete_ref("", "MERGE_AUTOSTASH", &stash_oid, REF_NO_DEREF);
 
 		/* Invoke 'git reset --merge' */
 		ret = cmd_reset(nargc, nargv, prefix);
 
-		if (stash_oid.len)
-			apply_autostash_oid(stash_oid.buf);
+		if (!is_null_oid(&stash_oid)) {
+			oid_to_hex_r(stash_oid_hex, &stash_oid);
+			apply_autostash_oid(stash_oid_hex);
+		}
 
-		strbuf_release(&stash_oid);
 		goto done;
 	}
 
@@ -1563,13 +1564,12 @@ int cmd_merge(int argc, const char **argv, const char *prefix)
 		}
 
 		if (autostash)
-			create_autostash(the_repository,
-					 git_path_merge_autostash(the_repository));
+			create_autostash_ref(the_repository, "MERGE_AUTOSTASH");
 		if (checkout_fast_forward(the_repository,
 					  &head_commit->object.oid,
 					  &commit->object.oid,
 					  overwrite_ignore)) {
-			apply_autostash(git_path_merge_autostash(the_repository));
+			apply_autostash_ref(the_repository, "MERGE_AUTOSTASH");
 			ret = 1;
 			goto done;
 		}
@@ -1655,8 +1655,7 @@ int cmd_merge(int argc, const char **argv, const char *prefix)
 		die_ff_impossible();
 
 	if (autostash)
-		create_autostash(the_repository,
-				 git_path_merge_autostash(the_repository));
+		create_autostash_ref(the_repository, "MERGE_AUTOSTASH");
 
 	/* We are going to make a new commit. */
 	git_committer_info(IDENT_STRICT);
@@ -1741,7 +1740,7 @@ int cmd_merge(int argc, const char **argv, const char *prefix)
 		else
 			fprintf(stderr, _("Merge with strategy %s failed.\n"),
 				use_strategies[0]->name);
-		apply_autostash(git_path_merge_autostash(the_repository));
+		apply_autostash_ref(the_repository, "MERGE_AUTOSTASH");
 		ret = 2;
 		goto done;
 	} else if (best_strategy == wt_strategy)
diff --git a/builtin/pack-objects.c b/builtin/pack-objects.c
index 5c8bfe1..329aeac 100644
--- a/builtin/pack-objects.c
+++ b/builtin/pack-objects.c
@@ -218,13 +218,19 @@ static int thin;
 static int num_preferred_base;
 static struct progress *progress_state;
 
-static struct packed_git *reuse_packfile;
+static struct bitmapped_pack *reuse_packfiles;
+static size_t reuse_packfiles_nr;
+static size_t reuse_packfiles_used_nr;
 static uint32_t reuse_packfile_objects;
 static struct bitmap *reuse_packfile_bitmap;
 
 static int use_bitmap_index_default = 1;
 static int use_bitmap_index = -1;
-static int allow_pack_reuse = 1;
+static enum {
+	NO_PACK_REUSE = 0,
+	SINGLE_PACK_REUSE,
+	MULTI_PACK_REUSE,
+} allow_pack_reuse = SINGLE_PACK_REUSE;
 static enum {
 	WRITE_BITMAP_FALSE = 0,
 	WRITE_BITMAP_QUIET,
@@ -1010,7 +1016,9 @@ static off_t find_reused_offset(off_t where)
 	return reused_chunks[lo-1].difference;
 }
 
-static void write_reused_pack_one(size_t pos, struct hashfile *out,
+static void write_reused_pack_one(struct packed_git *reuse_packfile,
+				  size_t pos, struct hashfile *out,
+				  off_t pack_start,
 				  struct pack_window **w_curs)
 {
 	off_t offset, next, cur;
@@ -1020,7 +1028,8 @@ static void write_reused_pack_one(size_t pos, struct hashfile *out,
 	offset = pack_pos_to_offset(reuse_packfile, pos);
 	next = pack_pos_to_offset(reuse_packfile, pos + 1);
 
-	record_reused_object(offset, offset - hashfile_total(out));
+	record_reused_object(offset,
+			     offset - (hashfile_total(out) - pack_start));
 
 	cur = offset;
 	type = unpack_object_header(reuse_packfile, w_curs, &cur, &size);
@@ -1088,41 +1097,93 @@ static void write_reused_pack_one(size_t pos, struct hashfile *out,
 	copy_pack_data(out, reuse_packfile, w_curs, offset, next - offset);
 }
 
-static size_t write_reused_pack_verbatim(struct hashfile *out,
+static size_t write_reused_pack_verbatim(struct bitmapped_pack *reuse_packfile,
+					 struct hashfile *out,
+					 off_t pack_start,
 					 struct pack_window **w_curs)
 {
-	size_t pos = 0;
+	size_t pos = reuse_packfile->bitmap_pos;
+	size_t end;
 
-	while (pos < reuse_packfile_bitmap->word_alloc &&
-			reuse_packfile_bitmap->words[pos] == (eword_t)~0)
-		pos++;
+	if (pos % BITS_IN_EWORD) {
+		size_t word_pos = (pos / BITS_IN_EWORD);
+		size_t offset = pos % BITS_IN_EWORD;
+		size_t last;
+		eword_t word = reuse_packfile_bitmap->words[word_pos];
 
-	if (pos) {
-		off_t to_write;
+		if (offset + reuse_packfile->bitmap_nr < BITS_IN_EWORD)
+			last = offset + reuse_packfile->bitmap_nr;
+		else
+			last = BITS_IN_EWORD;
 
-		written = (pos * BITS_IN_EWORD);
-		to_write = pack_pos_to_offset(reuse_packfile, written)
-			- sizeof(struct pack_header);
+		for (; offset < last; offset++) {
+			if (word >> offset == 0)
+				return word_pos;
+			if (!bitmap_get(reuse_packfile_bitmap,
+					word_pos * BITS_IN_EWORD + offset))
+				return word_pos;
+		}
+
+		pos += BITS_IN_EWORD - (pos % BITS_IN_EWORD);
+	}
+
+	/*
+	 * Now we're going to copy as many whole eword_t's as possible.
+	 * "end" is the index of the last whole eword_t we copy, but
+	 * there may be additional bits to process. Those are handled
+	 * individually by write_reused_pack().
+	 *
+	 * Begin by advancing to the first word boundary in range of the
+	 * bit positions occupied by objects in "reuse_packfile". Then
+	 * pick the last word boundary in the same range. If we have at
+	 * least one word's worth of bits to process, continue on.
+	 */
+	end = reuse_packfile->bitmap_pos + reuse_packfile->bitmap_nr;
+	if (end % BITS_IN_EWORD)
+		end -= end % BITS_IN_EWORD;
+	if (pos >= end)
+		return reuse_packfile->bitmap_pos / BITS_IN_EWORD;
+
+	while (pos < end &&
+	       reuse_packfile_bitmap->words[pos / BITS_IN_EWORD] == (eword_t)~0)
+		pos += BITS_IN_EWORD;
+
+	if (pos > end)
+		pos = end;
+
+	if (reuse_packfile->bitmap_pos < pos) {
+		off_t pack_start_off = pack_pos_to_offset(reuse_packfile->p, 0);
+		off_t pack_end_off = pack_pos_to_offset(reuse_packfile->p,
+							pos - reuse_packfile->bitmap_pos);
+
+		written += pos - reuse_packfile->bitmap_pos;
 
 		/* We're recording one chunk, not one object. */
-		record_reused_object(sizeof(struct pack_header), 0);
+		record_reused_object(pack_start_off,
+				     pack_start_off - (hashfile_total(out) - pack_start));
 		hashflush(out);
-		copy_pack_data(out, reuse_packfile, w_curs,
-			sizeof(struct pack_header), to_write);
+		copy_pack_data(out, reuse_packfile->p, w_curs,
+			pack_start_off, pack_end_off - pack_start_off);
 
 		display_progress(progress_state, written);
 	}
-	return pos;
+	if (pos % BITS_IN_EWORD)
+		BUG("attempted to jump past a word boundary to %"PRIuMAX,
+		    (uintmax_t)pos);
+	return pos / BITS_IN_EWORD;
 }
 
-static void write_reused_pack(struct hashfile *f)
+static void write_reused_pack(struct bitmapped_pack *reuse_packfile,
+			      struct hashfile *f)
 {
-	size_t i = 0;
+	size_t i = reuse_packfile->bitmap_pos / BITS_IN_EWORD;
 	uint32_t offset;
+	off_t pack_start = hashfile_total(f) - sizeof(struct pack_header);
 	struct pack_window *w_curs = NULL;
 
 	if (allow_ofs_delta)
-		i = write_reused_pack_verbatim(f, &w_curs);
+		i = write_reused_pack_verbatim(reuse_packfile, f, pack_start,
+					       &w_curs);
 
 	for (; i < reuse_packfile_bitmap->word_alloc; ++i) {
 		eword_t word = reuse_packfile_bitmap->words[i];
@@ -1133,16 +1194,23 @@ static void write_reused_pack(struct hashfile *f)
 				break;
 
 			offset += ewah_bit_ctz64(word >> offset);
+			if (pos + offset < reuse_packfile->bitmap_pos)
+				continue;
+			if (pos + offset >= reuse_packfile->bitmap_pos + reuse_packfile->bitmap_nr)
+				goto done;
 			/*
 			 * Can use bit positions directly, even for MIDX
 			 * bitmaps. See comment in try_partial_reuse()
 			 * for why.
 			 */
-			write_reused_pack_one(pos + offset, f, &w_curs);
+			write_reused_pack_one(reuse_packfile->p,
+					      pos + offset - reuse_packfile->bitmap_pos,
+					      f, pack_start, &w_curs);
 			display_progress(progress_state, ++written);
 		}
 	}
 
+done:
 	unuse_pack(&w_curs);
 }
 
@@ -1194,9 +1262,14 @@ static void write_pack_file(void)
 
 		offset = write_pack_header(f, nr_remaining);
 
-		if (reuse_packfile) {
+		if (reuse_packfiles_nr) {
 			assert(pack_to_stdout);
-			write_reused_pack(f);
+			for (j = 0; j < reuse_packfiles_nr; j++) {
+				reused_chunks_nr = 0;
+				write_reused_pack(&reuse_packfiles[j], f);
+				if (reused_chunks_nr)
+					reuse_packfiles_used_nr++;
+			}
 			offset = hashfile_total(f);
 		}
 
@@ -3172,7 +3245,19 @@ static int git_pack_config(const char *k, const char *v,
 		return 0;
 	}
 	if (!strcmp(k, "pack.allowpackreuse")) {
-		allow_pack_reuse = git_config_bool(k, v);
+		int res = git_parse_maybe_bool_text(v);
+		if (res < 0) {
+			if (!strcasecmp(v, "single"))
+				allow_pack_reuse = SINGLE_PACK_REUSE;
+			else if (!strcasecmp(v, "multi"))
+				allow_pack_reuse = MULTI_PACK_REUSE;
+			else
+				die(_("invalid pack.allowPackReuse value: '%s'"), v);
+		} else if (res) {
+			allow_pack_reuse = SINGLE_PACK_REUSE;
+		} else {
+			allow_pack_reuse = NO_PACK_REUSE;
+		}
 		return 0;
 	}
 	if (!strcmp(k, "pack.threads")) {
@@ -3931,7 +4016,7 @@ static void loosen_unused_packed_objects(void)
  */
 static int pack_options_allow_reuse(void)
 {
-	return allow_pack_reuse &&
+	return allow_pack_reuse != NO_PACK_REUSE &&
 	       pack_to_stdout &&
 	       !ignore_packed_keep_on_disk &&
 	       !ignore_packed_keep_in_core &&
@@ -3944,13 +4029,18 @@ static int get_object_list_from_bitmap(struct rev_info *revs)
 	if (!(bitmap_git = prepare_bitmap_walk(revs, 0)))
 		return -1;
 
-	if (pack_options_allow_reuse() &&
-	    !reuse_partial_packfile_from_bitmap(
-			bitmap_git,
-			&reuse_packfile,
-			&reuse_packfile_objects,
-			&reuse_packfile_bitmap)) {
-		assert(reuse_packfile_objects);
+	if (pack_options_allow_reuse())
+		reuse_partial_packfile_from_bitmap(bitmap_git,
+						   &reuse_packfiles,
+						   &reuse_packfiles_nr,
+						   &reuse_packfile_bitmap,
+						   allow_pack_reuse == MULTI_PACK_REUSE);
+
+	if (reuse_packfiles) {
+		reuse_packfile_objects = bitmap_popcount(reuse_packfile_bitmap);
+		if (!reuse_packfile_objects)
+			BUG("expected non-empty reuse bitmap");
+
 		nr_result += reuse_packfile_objects;
 		nr_seen += reuse_packfile_objects;
 		display_progress(progress_state, nr_seen);
@@ -4306,6 +4396,8 @@ int cmd_pack_objects(int argc, const char **argv, const char *prefix)
 		prepare_repo_settings(the_repository);
 		if (sparse < 0)
 			sparse = the_repository->settings.pack_use_sparse;
+		if (the_repository->settings.pack_use_multi_pack_reuse)
+			allow_pack_reuse = MULTI_PACK_REUSE;
 	}
 
 	reset_pack_idx_option(&pack_idx_opts);
@@ -4518,11 +4610,20 @@ int cmd_pack_objects(int argc, const char **argv, const char *prefix)
 		fprintf_ln(stderr,
 			   _("Total %"PRIu32" (delta %"PRIu32"),"
 			     " reused %"PRIu32" (delta %"PRIu32"),"
-			     " pack-reused %"PRIu32),
+			     " pack-reused %"PRIu32" (from %"PRIuMAX")"),
 			   written, written_delta, reused, reused_delta,
-			   reuse_packfile_objects);
+			   reuse_packfile_objects,
+			   (uintmax_t)reuse_packfiles_used_nr);
+
+	trace2_data_intmax("pack-objects", the_repository, "written", written);
+	trace2_data_intmax("pack-objects", the_repository, "written/delta", written_delta);
+	trace2_data_intmax("pack-objects", the_repository, "reused", reused);
+	trace2_data_intmax("pack-objects", the_repository, "reused/delta", reused_delta);
+	trace2_data_intmax("pack-objects", the_repository, "pack-reused", reuse_packfile_objects);
+	trace2_data_intmax("pack-objects", the_repository, "packs-reused", reuse_packfiles_used_nr);
 
 cleanup:
+	clear_packing_data(&to_pack);
 	list_objects_filter_release(&filter_options);
 	strvec_clear(&rp);
 
diff --git a/builtin/rebase.c b/builtin/rebase.c
index 4084a6a..5b086f6 100644
--- a/builtin/rebase.c
+++ b/builtin/rebase.c
@@ -145,7 +145,6 @@ struct rebase_options {
 		.reapply_cherry_picks = -1,             \
 		.allow_empty_message = 1,               \
 		.autosquash = -1,                       \
-		.config_autosquash = -1,                \
 		.rebase_merges = -1,                    \
 		.config_rebase_merges = -1,             \
 		.update_refs = -1,                      \
@@ -516,7 +515,7 @@ static int finish_rebase(struct rebase_options *opts)
 	int ret = 0;
 
 	delete_ref(NULL, "REBASE_HEAD", NULL, REF_NO_DEREF);
-	unlink(git_path_auto_merge(the_repository));
+	delete_ref(NULL, "AUTO_MERGE", NULL, REF_NO_DEREF);
 	apply_autostash(state_dir_path("autostash", opts));
 	/*
 	 * We ignore errors in 'git maintenance run --auto', since the
@@ -702,10 +701,8 @@ static int run_specific_rebase(struct rebase_options *opts)
 	if (opts->type == REBASE_MERGE) {
 		/* Run sequencer-based rebase */
 		setenv("GIT_CHERRY_PICK_HELP", resolvemsg, 1);
-		if (!(opts->flags & REBASE_INTERACTIVE_EXPLICIT)) {
+		if (!(opts->flags & REBASE_INTERACTIVE_EXPLICIT))
 			setenv("GIT_SEQUENCE_EDITOR", ":", 1);
-			opts->autosquash = 0;
-		}
 		if (opts->gpg_sign_opt) {
 			/* remove the leading "-S" */
 			char *tmp = xstrdup(opts->gpg_sign_opt + 2);
@@ -1396,7 +1393,6 @@ int cmd_rebase(int argc, const char **argv, const char *prefix)
 	if ((options.flags & REBASE_INTERACTIVE_EXPLICIT) ||
 	    (options.action != ACTION_NONE) ||
 	    (options.exec.nr > 0) ||
-	    (options.autosquash == -1 && options.config_autosquash == 1) ||
 	    options.autosquash == 1) {
 		allow_preemptive_ff = 0;
 	}
@@ -1499,8 +1495,6 @@ int cmd_rebase(int argc, const char **argv, const char *prefix)
 			if (is_merge(&options))
 				die(_("apply options and merge options "
 					  "cannot be used together"));
-			else if (options.autosquash == -1 && options.config_autosquash == 1)
-				die(_("apply options are incompatible with rebase.autoSquash.  Consider adding --no-autosquash"));
 			else if (options.rebase_merges == -1 && options.config_rebase_merges == 1)
 				die(_("apply options are incompatible with rebase.rebaseMerges.  Consider adding --no-rebase-merges"));
 			else if (options.update_refs == -1 && options.config_update_refs == 1)
@@ -1520,10 +1514,13 @@ int cmd_rebase(int argc, const char **argv, const char *prefix)
 	options.rebase_merges = (options.rebase_merges >= 0) ? options.rebase_merges :
 				((options.config_rebase_merges >= 0) ? options.config_rebase_merges : 0);
 
-	if (options.autosquash == 1)
+	if (options.autosquash == 1) {
 		imply_merge(&options, "--autosquash");
-	options.autosquash = (options.autosquash >= 0) ? options.autosquash :
-			     ((options.config_autosquash >= 0) ? options.config_autosquash : 0);
+	} else if (options.autosquash == -1) {
+		options.autosquash =
+			options.config_autosquash &&
+			(options.flags & REBASE_INTERACTIVE_EXPLICIT);
+	}
 
 	if (options.type == REBASE_UNSPECIFIED) {
 		if (!strcmp(options.default_backend, "merge"))
diff --git a/builtin/replay.c b/builtin/replay.c
new file mode 100644
index 0000000..6bc4b47
--- /dev/null
+++ b/builtin/replay.c
@@ -0,0 +1,446 @@
+/*
+ * "git replay" builtin command
+ */
+
+#define USE_THE_INDEX_VARIABLE
+#include "git-compat-util.h"
+
+#include "builtin.h"
+#include "environment.h"
+#include "hex.h"
+#include "lockfile.h"
+#include "merge-ort.h"
+#include "object-name.h"
+#include "parse-options.h"
+#include "refs.h"
+#include "revision.h"
+#include "strmap.h"
+#include <oidset.h>
+#include <tree.h>
+
+static const char *short_commit_name(struct commit *commit)
+{
+	return repo_find_unique_abbrev(the_repository, &commit->object.oid,
+				       DEFAULT_ABBREV);
+}
+
+static struct commit *peel_committish(const char *name)
+{
+	struct object *obj;
+	struct object_id oid;
+
+	if (repo_get_oid(the_repository, name, &oid))
+		return NULL;
+	obj = parse_object(the_repository, &oid);
+	return (struct commit *)repo_peel_to_type(the_repository, name, 0, obj,
+						  OBJ_COMMIT);
+}
+
+static char *get_author(const char *message)
+{
+	size_t len;
+	const char *a;
+
+	a = find_commit_header(message, "author", &len);
+	if (a)
+		return xmemdupz(a, len);
+
+	return NULL;
+}
+
+static struct commit *create_commit(struct tree *tree,
+				    struct commit *based_on,
+				    struct commit *parent)
+{
+	struct object_id ret;
+	struct object *obj;
+	struct commit_list *parents = NULL;
+	char *author;
+	char *sign_commit = NULL; /* FIXME: cli users might want to sign again */
+	struct commit_extra_header *extra;
+	struct strbuf msg = STRBUF_INIT;
+	const char *out_enc = get_commit_output_encoding();
+	const char *message = repo_logmsg_reencode(the_repository, based_on,
+						   NULL, out_enc);
+	const char *orig_message = NULL;
+	const char *exclude_gpgsig[] = { "gpgsig", NULL };
+
+	commit_list_insert(parent, &parents);
+	extra = read_commit_extra_headers(based_on, exclude_gpgsig);
+	find_commit_subject(message, &orig_message);
+	strbuf_addstr(&msg, orig_message);
+	author = get_author(message);
+	reset_ident_date();
+	if (commit_tree_extended(msg.buf, msg.len, &tree->object.oid, parents,
+				 &ret, author, NULL, sign_commit, extra)) {
+		error(_("failed to write commit object"));
+		return NULL;
+	}
+	free(author);
+	strbuf_release(&msg);
+
+	obj = parse_object(the_repository, &ret);
+	return (struct commit *)obj;
+}
+
+struct ref_info {
+	struct commit *onto;
+	struct strset positive_refs;
+	struct strset negative_refs;
+	int positive_refexprs;
+	int negative_refexprs;
+};
+
+static void get_ref_information(struct rev_cmdline_info *cmd_info,
+				struct ref_info *ref_info)
+{
+	int i;
+
+	ref_info->onto = NULL;
+	strset_init(&ref_info->positive_refs);
+	strset_init(&ref_info->negative_refs);
+	ref_info->positive_refexprs = 0;
+	ref_info->negative_refexprs = 0;
+
+	/*
+	 * When the user specifies e.g.
+	 *   git replay origin/main..mybranch
+	 *   git replay ^origin/next mybranch1 mybranch2
+	 * we want to be able to determine where to replay the commits.  In
+	 * these examples, the branches are probably based on an old version
+	 * of either origin/main or origin/next, so we want to replay on the
+	 * newest version of that branch.  In contrast we would want to error
+	 * out if they ran
+	 *   git replay ^origin/master ^origin/next mybranch
+	 *   git replay mybranch~2..mybranch
+	 * the first of those because there's no unique base to choose, and
+	 * the second because they'd likely just be replaying commits on top
+	 * of the same commit and not making any difference.
+	 */
+	for (i = 0; i < cmd_info->nr; i++) {
+		struct rev_cmdline_entry *e = cmd_info->rev + i;
+		struct object_id oid;
+		const char *refexpr = e->name;
+		char *fullname = NULL;
+		int can_uniquely_dwim = 1;
+
+		if (*refexpr == '^')
+			refexpr++;
+		if (repo_dwim_ref(the_repository, refexpr, strlen(refexpr), &oid, &fullname, 0) != 1)
+			can_uniquely_dwim = 0;
+
+		if (e->flags & BOTTOM) {
+			if (can_uniquely_dwim)
+				strset_add(&ref_info->negative_refs, fullname);
+			if (!ref_info->negative_refexprs)
+				ref_info->onto = lookup_commit_reference_gently(the_repository,
+										&e->item->oid, 1);
+			ref_info->negative_refexprs++;
+		} else {
+			if (can_uniquely_dwim)
+				strset_add(&ref_info->positive_refs, fullname);
+			ref_info->positive_refexprs++;
+		}
+
+		free(fullname);
+	}
+}
+
+static void determine_replay_mode(struct rev_cmdline_info *cmd_info,
+				  const char *onto_name,
+				  const char **advance_name,
+				  struct commit **onto,
+				  struct strset **update_refs)
+{
+	struct ref_info rinfo;
+
+	get_ref_information(cmd_info, &rinfo);
+	if (!rinfo.positive_refexprs)
+		die(_("need some commits to replay"));
+	if (onto_name && *advance_name)
+		die(_("--onto and --advance are incompatible"));
+	else if (onto_name) {
+		*onto = peel_committish(onto_name);
+		if (rinfo.positive_refexprs <
+		    strset_get_size(&rinfo.positive_refs))
+			die(_("all positive revisions given must be references"));
+	} else if (*advance_name) {
+		struct object_id oid;
+		char *fullname = NULL;
+
+		*onto = peel_committish(*advance_name);
+		if (repo_dwim_ref(the_repository, *advance_name, strlen(*advance_name),
+			     &oid, &fullname, 0) == 1) {
+			*advance_name = fullname;
+		} else {
+			die(_("argument to --advance must be a reference"));
+		}
+		if (rinfo.positive_refexprs > 1)
+			die(_("cannot advance target with multiple sources because ordering would be ill-defined"));
+	} else {
+		int positive_refs_complete = (
+			rinfo.positive_refexprs ==
+			strset_get_size(&rinfo.positive_refs));
+		int negative_refs_complete = (
+			rinfo.negative_refexprs ==
+			strset_get_size(&rinfo.negative_refs));
+		/*
+		 * We need either positive_refs_complete or
+		 * negative_refs_complete, but not both.
+		 */
+		if (rinfo.negative_refexprs > 0 &&
+		    positive_refs_complete == negative_refs_complete)
+			die(_("cannot implicitly determine whether this is an --advance or --onto operation"));
+		if (negative_refs_complete) {
+			struct hashmap_iter iter;
+			struct strmap_entry *entry;
+
+			if (rinfo.negative_refexprs == 0)
+				die(_("all positive revisions given must be references"));
+			else if (rinfo.negative_refexprs > 1)
+				die(_("cannot implicitly determine whether this is an --advance or --onto operation"));
+			else if (rinfo.positive_refexprs > 1)
+				die(_("cannot advance target with multiple source branches because ordering would be ill-defined"));
+
+			/* Only one entry, but we have to loop to get it */
+			strset_for_each_entry(&rinfo.negative_refs,
+					      &iter, entry) {
+				*advance_name = entry->key;
+			}
+		} else { /* positive_refs_complete */
+			if (rinfo.negative_refexprs > 1)
+				die(_("cannot implicitly determine correct base for --onto"));
+			if (rinfo.negative_refexprs == 1)
+				*onto = rinfo.onto;
+		}
+	}
+	if (!*advance_name) {
+		*update_refs = xcalloc(1, sizeof(**update_refs));
+		**update_refs = rinfo.positive_refs;
+		memset(&rinfo.positive_refs, 0, sizeof(**update_refs));
+	}
+	strset_clear(&rinfo.negative_refs);
+	strset_clear(&rinfo.positive_refs);
+}
+
+static struct commit *mapped_commit(kh_oid_map_t *replayed_commits,
+				    struct commit *commit,
+				    struct commit *fallback)
+{
+	khint_t pos = kh_get_oid_map(replayed_commits, commit->object.oid);
+	if (pos == kh_end(replayed_commits))
+		return fallback;
+	return kh_value(replayed_commits, pos);
+}
+
+static struct commit *pick_regular_commit(struct commit *pickme,
+					  kh_oid_map_t *replayed_commits,
+					  struct commit *onto,
+					  struct merge_options *merge_opt,
+					  struct merge_result *result)
+{
+	struct commit *base, *replayed_base;
+	struct tree *pickme_tree, *base_tree;
+
+	base = pickme->parents->item;
+	replayed_base = mapped_commit(replayed_commits, base, onto);
+
+	result->tree = repo_get_commit_tree(the_repository, replayed_base);
+	pickme_tree = repo_get_commit_tree(the_repository, pickme);
+	base_tree = repo_get_commit_tree(the_repository, base);
+
+	merge_opt->branch1 = short_commit_name(replayed_base);
+	merge_opt->branch2 = short_commit_name(pickme);
+	merge_opt->ancestor = xstrfmt("parent of %s", merge_opt->branch2);
+
+	merge_incore_nonrecursive(merge_opt,
+				  base_tree,
+				  result->tree,
+				  pickme_tree,
+				  result);
+
+	free((char*)merge_opt->ancestor);
+	merge_opt->ancestor = NULL;
+	if (!result->clean)
+		return NULL;
+	return create_commit(result->tree, pickme, replayed_base);
+}
+
+int cmd_replay(int argc, const char **argv, const char *prefix)
+{
+	const char *advance_name = NULL;
+	struct commit *onto = NULL;
+	const char *onto_name = NULL;
+	int contained = 0;
+
+	struct rev_info revs;
+	struct commit *last_commit = NULL;
+	struct commit *commit;
+	struct merge_options merge_opt;
+	struct merge_result result;
+	struct strset *update_refs = NULL;
+	kh_oid_map_t *replayed_commits;
+	int ret = 0;
+
+	const char * const replay_usage[] = {
+		N_("(EXPERIMENTAL!) git replay "
+		   "([--contained] --onto <newbase> | --advance <branch>) "
+		   "<revision-range>..."),
+		NULL
+	};
+	struct option replay_options[] = {
+		OPT_STRING(0, "advance", &advance_name,
+			   N_("branch"),
+			   N_("make replay advance given branch")),
+		OPT_STRING(0, "onto", &onto_name,
+			   N_("revision"),
+			   N_("replay onto given commit")),
+		OPT_BOOL(0, "contained", &contained,
+			 N_("advance all branches contained in revision-range")),
+		OPT_END()
+	};
+
+	argc = parse_options(argc, argv, prefix, replay_options, replay_usage,
+			     PARSE_OPT_KEEP_ARGV0 | PARSE_OPT_KEEP_UNKNOWN_OPT);
+
+	if (!onto_name && !advance_name) {
+		error(_("option --onto or --advance is mandatory"));
+		usage_with_options(replay_usage, replay_options);
+	}
+
+	if (advance_name && contained)
+		die(_("options '%s' and '%s' cannot be used together"),
+		    "--advance", "--contained");
+
+	repo_init_revisions(the_repository, &revs, prefix);
+
+	/*
+	 * Set desired values for rev walking options here. If they
+	 * are changed by some user specified option in setup_revisions()
+	 * below, we will detect that below and then warn.
+	 *
+	 * TODO: In the future we might want to either die(), or allow
+	 * some options changing these values if we think they could
+	 * be useful.
+	 */
+	revs.reverse = 1;
+	revs.sort_order = REV_SORT_IN_GRAPH_ORDER;
+	revs.topo_order = 1;
+	revs.simplify_history = 0;
+
+	argc = setup_revisions(argc, argv, &revs, NULL);
+	if (argc > 1) {
+		ret = error(_("unrecognized argument: %s"), argv[1]);
+		goto cleanup;
+	}
+
+	/*
+	 * Detect and warn if we override some user specified rev
+	 * walking options.
+	 */
+	if (revs.reverse != 1) {
+		warning(_("some rev walking options will be overridden as "
+			  "'%s' bit in 'struct rev_info' will be forced"),
+			"reverse");
+		revs.reverse = 1;
+	}
+	if (revs.sort_order != REV_SORT_IN_GRAPH_ORDER) {
+		warning(_("some rev walking options will be overridden as "
+			  "'%s' bit in 'struct rev_info' will be forced"),
+			"sort_order");
+		revs.sort_order = REV_SORT_IN_GRAPH_ORDER;
+	}
+	if (revs.topo_order != 1) {
+		warning(_("some rev walking options will be overridden as "
+			  "'%s' bit in 'struct rev_info' will be forced"),
+			"topo_order");
+		revs.topo_order = 1;
+	}
+	if (revs.simplify_history != 0) {
+		warning(_("some rev walking options will be overridden as "
+			  "'%s' bit in 'struct rev_info' will be forced"),
+			"simplify_history");
+		revs.simplify_history = 0;
+	}
+
+	determine_replay_mode(&revs.cmdline, onto_name, &advance_name,
+			      &onto, &update_refs);
+
+	if (!onto) /* FIXME: Should handle replaying down to root commit */
+		die("Replaying down to root commit is not supported yet!");
+
+	if (prepare_revision_walk(&revs) < 0) {
+		ret = error(_("error preparing revisions"));
+		goto cleanup;
+	}
+
+	init_merge_options(&merge_opt, the_repository);
+	memset(&result, 0, sizeof(result));
+	merge_opt.show_rename_progress = 0;
+	last_commit = onto;
+	replayed_commits = kh_init_oid_map();
+	while ((commit = get_revision(&revs))) {
+		const struct name_decoration *decoration;
+		khint_t pos;
+		int hr;
+
+		if (!commit->parents)
+			die(_("replaying down to root commit is not supported yet!"));
+		if (commit->parents->next)
+			die(_("replaying merge commits is not supported yet!"));
+
+		last_commit = pick_regular_commit(commit, replayed_commits, onto,
+						  &merge_opt, &result);
+		if (!last_commit)
+			break;
+
+		/* Record commit -> last_commit mapping */
+		pos = kh_put_oid_map(replayed_commits, commit->object.oid, &hr);
+		if (hr == 0)
+			BUG("Duplicate rewritten commit: %s\n",
+			    oid_to_hex(&commit->object.oid));
+		kh_value(replayed_commits, pos) = last_commit;
+
+		/* Update any necessary branches */
+		if (advance_name)
+			continue;
+		decoration = get_name_decoration(&commit->object);
+		if (!decoration)
+			continue;
+		while (decoration) {
+			if (decoration->type == DECORATION_REF_LOCAL &&
+			    (contained || strset_contains(update_refs,
+							  decoration->name))) {
+				printf("update %s %s %s\n",
+				       decoration->name,
+				       oid_to_hex(&last_commit->object.oid),
+				       oid_to_hex(&commit->object.oid));
+			}
+			decoration = decoration->next;
+		}
+	}
+
+	/* In --advance mode, advance the target ref */
+	if (result.clean == 1 && advance_name) {
+		printf("update %s %s %s\n",
+		       advance_name,
+		       oid_to_hex(&last_commit->object.oid),
+		       oid_to_hex(&onto->object.oid));
+	}
+
+	merge_finalize(&merge_opt, &result);
+	kh_destroy_oid_map(replayed_commits);
+	if (update_refs) {
+		strset_clear(update_refs);
+		free(update_refs);
+	}
+	ret = result.clean;
+
+cleanup:
+	release_revisions(&revs);
+
+	/* Return */
+	if (ret < 0)
+		exit(128);
+	return ret ? 0 : 1;
+}
diff --git a/builtin/rev-parse.c b/builtin/rev-parse.c
index 917f122..d089876 100644
--- a/builtin/rev-parse.c
+++ b/builtin/rev-parse.c
@@ -1062,6 +1062,10 @@ int cmd_rev_parse(int argc, const char **argv, const char *prefix)
 				puts(the_hash_algo->name);
 				continue;
 			}
+			if (!strcmp(arg, "--show-ref-format")) {
+				puts(ref_storage_format_to_name(the_repository->ref_storage_format));
+				continue;
+			}
 			if (!strcmp(arg, "--end-of-options")) {
 				seen_end_of_options = 1;
 				if (filter & (DO_FLAGS | DO_REVS))
diff --git a/builtin/send-pack.c b/builtin/send-pack.c
index b7183be..3df9eaa 100644
--- a/builtin/send-pack.c
+++ b/builtin/send-pack.c
@@ -333,6 +333,7 @@ int cmd_send_pack(int argc, const char **argv, const char *prefix)
 	}
 
 	if (!ret && !transport_refs_pushed(remote_refs))
+		/* stable plumbing output; do not modify or localize */
 		fprintf(stderr, "Everything up-to-date\n");
 
 	return ret;
diff --git a/builtin/show-ref.c b/builtin/show-ref.c
index 79955c2..1c15421 100644
--- a/builtin/show-ref.c
+++ b/builtin/show-ref.c
@@ -172,7 +172,7 @@ static int cmd_show_ref__verify(const struct show_one_options *show_one_opts,
 	while (*refs) {
 		struct object_id oid;
 
-		if ((starts_with(*refs, "refs/") || !strcmp(*refs, "HEAD")) &&
+		if ((starts_with(*refs, "refs/") || refname_is_safe(*refs)) &&
 		    !read_ref(*refs, &oid)) {
 			show_one(show_one_opts, *refs, &oid);
 		}
diff --git a/builtin/sparse-checkout.c b/builtin/sparse-checkout.c
index 288a832..0f52e25 100644
--- a/builtin/sparse-checkout.c
+++ b/builtin/sparse-checkout.c
@@ -773,8 +773,7 @@ static int sparse_checkout_add(int argc, const char **argv, const char *prefix)
 
 	argc = parse_options(argc, argv, prefix,
 			     builtin_sparse_checkout_add_options,
-			     builtin_sparse_checkout_add_usage,
-			     PARSE_OPT_KEEP_UNKNOWN_OPT);
+			     builtin_sparse_checkout_add_usage, 0);
 
 	sanitize_paths(argc, argv, prefix, add_opts.skip_checks);
 
@@ -820,8 +819,7 @@ static int sparse_checkout_set(int argc, const char **argv, const char *prefix)
 
 	argc = parse_options(argc, argv, prefix,
 			     builtin_sparse_checkout_set_options,
-			     builtin_sparse_checkout_set_usage,
-			     PARSE_OPT_KEEP_UNKNOWN_OPT);
+			     builtin_sparse_checkout_set_usage, 0);
 
 	if (update_modes(&set_opts.cone_mode, &set_opts.sparse_index))
 		return 1;
@@ -992,8 +990,7 @@ static int sparse_checkout_check_rules(int argc, const char **argv, const char *
 
 	argc = parse_options(argc, argv, prefix,
 			     builtin_sparse_checkout_check_rules_options,
-			     builtin_sparse_checkout_check_rules_usage,
-			     PARSE_OPT_KEEP_UNKNOWN_OPT);
+			     builtin_sparse_checkout_check_rules_usage, 0);
 
 	if (check_rules_opts.rules_file && check_rules_opts.cone_mode < 0)
 		check_rules_opts.cone_mode = 1;
diff --git a/builtin/tag.c b/builtin/tag.c
index 79ca53c..37473ac 100644
--- a/builtin/tag.c
+++ b/builtin/tag.c
@@ -43,18 +43,11 @@ static const char * const git_tag_usage[] = {
 static unsigned int colopts;
 static int force_sign_annotate;
 static int config_sign_tag = -1; /* unspecified */
-static int omit_empty = 0;
 
 static int list_tags(struct ref_filter *filter, struct ref_sorting *sorting,
 		     struct ref_format *format)
 {
-	struct ref_array array;
-	struct strbuf output = STRBUF_INIT;
-	struct strbuf err = STRBUF_INIT;
 	char *to_free = NULL;
-	int i;
-
-	memset(&array, 0, sizeof(array));
 
 	if (filter->lines == -1)
 		filter->lines = 0;
@@ -72,23 +65,8 @@ static int list_tags(struct ref_filter *filter, struct ref_sorting *sorting,
 	if (verify_ref_format(format))
 		die(_("unable to parse format string"));
 	filter->with_commit_tag_algo = 1;
-	filter_refs(&array, filter, FILTER_REFS_TAGS);
-	filter_ahead_behind(the_repository, format, &array);
-	ref_array_sort(sorting, &array);
+	filter_and_format_refs(filter, FILTER_REFS_TAGS, sorting, format);
 
-	for (i = 0; i < array.nr; i++) {
-		strbuf_reset(&output);
-		strbuf_reset(&err);
-		if (format_ref_array_item(array.items[i], format, &output, &err))
-			die("%s", err.buf);
-		fwrite(output.buf, 1, output.len, stdout);
-		if (output.len || !omit_empty)
-			putchar('\n');
-	}
-
-	strbuf_release(&err);
-	strbuf_release(&output);
-	ref_array_clear(&array);
 	free(to_free);
 
 	return 0;
@@ -480,7 +458,7 @@ int cmd_tag(int argc, const char **argv, const char *prefix)
 		OPT_WITHOUT(&filter.no_commit, N_("print only tags that don't contain the commit")),
 		OPT_MERGED(&filter, N_("print only tags that are merged")),
 		OPT_NO_MERGED(&filter, N_("print only tags that are not merged")),
-		OPT_BOOL(0, "omit-empty",  &omit_empty,
+		OPT_BOOL(0, "omit-empty",  &format.array_opts.omit_empty,
 			N_("do not output a newline after empty formatted refs")),
 		OPT_REF_SORT(&sorting_options),
 		{
@@ -500,7 +478,13 @@ int cmd_tag(int argc, const char **argv, const char *prefix)
 
 	setup_ref_filter_porcelain_msg();
 
+	/*
+	 * Try to set sort keys from config. If config does not set any,
+	 * fall back on default (refname) sorting.
+	 */
 	git_config(git_tag_config, &sorting_options);
+	if (!sorting_options.nr)
+		string_list_append(&sorting_options, "refname");
 
 	memset(&opt, 0, sizeof(opt));
 	filter.lines = -1;
diff --git a/builtin/var.c b/builtin/var.c
index 8cf7dd9..cf55672 100644
--- a/builtin/var.c
+++ b/builtin/var.c
@@ -90,7 +90,7 @@ static char *git_config_val_global(int ident_flag UNUSED)
 	char *user, *xdg;
 	size_t unused;
 
-	git_global_config(&user, &xdg);
+	git_global_config_paths(&user, &xdg);
 	if (xdg && *xdg) {
 		normalize_path_copy(xdg, xdg);
 		strbuf_addf(&buf, "%s\n", xdg);
diff --git a/builtin/worktree.c b/builtin/worktree.c
index e1033c2..9c76b62 100644
--- a/builtin/worktree.c
+++ b/builtin/worktree.c
@@ -416,7 +416,6 @@ static int add_worktree(const char *path, const char *refname,
 	struct strbuf sb_git = STRBUF_INIT, sb_repo = STRBUF_INIT;
 	struct strbuf sb = STRBUF_INIT, realpath = STRBUF_INIT;
 	const char *name;
-	struct child_process cp = CHILD_PROCESS_INIT;
 	struct strvec child_env = STRVEC_INIT;
 	unsigned int counter = 0;
 	int len, ret;
@@ -424,7 +423,8 @@ static int add_worktree(const char *path, const char *refname,
 	struct commit *commit = NULL;
 	int is_branch = 0;
 	struct strbuf sb_name = STRBUF_INIT;
-	struct worktree **worktrees;
+	struct worktree **worktrees, *wt = NULL;
+	struct ref_store *wt_refs;
 
 	worktrees = get_worktrees();
 	check_candidate_path(path, opts->force, worktrees, "add");
@@ -495,21 +495,33 @@ static int add_worktree(const char *path, const char *refname,
 	strbuf_realpath(&realpath, get_git_common_dir(), 1);
 	write_file(sb_git.buf, "gitdir: %s/worktrees/%s",
 		   realpath.buf, name);
-	/*
-	 * This is to keep resolve_ref() happy. We need a valid HEAD
-	 * or is_git_directory() will reject the directory. Any value which
-	 * looks like an object ID will do since it will be immediately
-	 * replaced by the symbolic-ref or update-ref invocation in the new
-	 * worktree.
-	 */
-	strbuf_reset(&sb);
-	strbuf_addf(&sb, "%s/HEAD", sb_repo.buf);
-	write_file(sb.buf, "%s", oid_to_hex(null_oid()));
 	strbuf_reset(&sb);
 	strbuf_addf(&sb, "%s/commondir", sb_repo.buf);
 	write_file(sb.buf, "../..");
 
 	/*
+	 * Set up the ref store of the worktree and create the HEAD reference.
+	 */
+	wt = get_linked_worktree(name, 1);
+	if (!wt) {
+		ret = error(_("could not find created worktree '%s'"), name);
+		goto done;
+	}
+	wt_refs = get_worktree_ref_store(wt);
+
+	ret = refs_init_db(wt_refs, REFS_INIT_DB_IS_WORKTREE, &sb);
+	if (ret)
+		goto done;
+
+	if (!is_branch && commit)
+		ret = refs_update_ref(wt_refs, NULL, "HEAD", &commit->object.oid,
+				      NULL, 0, UPDATE_REFS_MSG_ON_ERR);
+	else
+		ret = refs_create_symref(wt_refs, "HEAD", symref.buf, NULL);
+	if (ret)
+		goto done;
+
+	/*
 	 * If the current worktree has sparse-checkout enabled, then copy
 	 * the sparse-checkout patterns from the current worktree.
 	 */
@@ -526,22 +538,6 @@ static int add_worktree(const char *path, const char *refname,
 
 	strvec_pushf(&child_env, "%s=%s", GIT_DIR_ENVIRONMENT, sb_git.buf);
 	strvec_pushf(&child_env, "%s=%s", GIT_WORK_TREE_ENVIRONMENT, path);
-	cp.git_cmd = 1;
-
-	if (!is_branch && commit) {
-		strvec_pushl(&cp.args, "update-ref", "HEAD",
-			     oid_to_hex(&commit->object.oid), NULL);
-	} else {
-		strvec_pushl(&cp.args, "symbolic-ref", "HEAD",
-			     symref.buf, NULL);
-		if (opts->quiet)
-			strvec_push(&cp.args, "--quiet");
-	}
-
-	strvec_pushv(&cp.env, child_env.v);
-	ret = run_command(&cp);
-	if (ret)
-		goto done;
 
 	if (opts->orphan &&
 	    (ret = make_worktree_orphan(refname, opts, &child_env)))
@@ -587,6 +583,7 @@ static int add_worktree(const char *path, const char *refname,
 	strbuf_release(&sb_git);
 	strbuf_release(&sb_name);
 	strbuf_release(&realpath);
+	free_worktree(wt);
 	return ret;
 }
 
diff --git a/ci/install-dependencies.sh b/ci/install-dependencies.sh
index 4f40753..b4e22de 100755
--- a/ci/install-dependencies.sh
+++ b/ci/install-dependencies.sh
@@ -37,15 +37,13 @@
 	test -z "$BREW_INSTALL_PACKAGES" ||
 	brew install $BREW_INSTALL_PACKAGES
 	brew link --force gettext
-	mkdir -p $HOME/bin
-	(
-		cd $HOME/bin
+
+	mkdir -p "$P4_PATH"
+	pushd "$P4_PATH"
 		wget -q "$P4WHENCE/bin.macosx1015x86_64/helix-core-server.tgz" &&
 		tar -xf helix-core-server.tgz &&
 		sudo xattr -d com.apple.quarantine p4 p4d 2>/dev/null || true
-	)
-	PATH="$PATH:${HOME}/bin"
-	export PATH
+	popd
 
 	if test -n "$CC_PACKAGE"
 	then
diff --git a/ci/install-docker-dependencies.sh b/ci/install-docker-dependencies.sh
index 48c43f0..eb2c9e1 100755
--- a/ci/install-docker-dependencies.sh
+++ b/ci/install-docker-dependencies.sh
@@ -21,7 +21,7 @@
 		apache2 apache2-http2 apache2-proxy apache2-ssl apache2-webdav apr-util-dbd_sqlite3 \
 		bash cvs gnupg perl-cgi perl-dbd-sqlite >/dev/null
 	;;
-linux-*)
+linux-*|StaticAnalysis)
 	# Required so that apt doesn't wait for user input on certain packages.
 	export DEBIAN_FRONTEND=noninteractive
 
@@ -31,6 +31,11 @@
 		perl-modules liberror-perl libauthen-sasl-perl libemail-valid-perl \
 		libdbd-sqlite3-perl libio-socket-ssl-perl libnet-smtp-ssl-perl ${CC_PACKAGE:-${CC:-gcc}} \
 		apache2 cvs cvsps gnupg libcgi-pm-perl subversion
+
+	if test "$jobname" = StaticAnalysis
+	then
+		apt install -q -y coccinelle
+	fi
 	;;
 pedantic)
 	dnf -yq update >/dev/null &&
diff --git a/ci/lib.sh b/ci/lib.sh
index c749b21..d5dd2f2 100755
--- a/ci/lib.sh
+++ b/ci/lib.sh
@@ -252,7 +252,14 @@
 	CI_COMMIT="$CI_COMMIT_SHA"
 	case "$CI_JOB_IMAGE" in
 	macos-*)
-		CI_OS_NAME=osx;;
+		# GitLab CI has Python installed via multiple package managers,
+		# most notably via asdf and Homebrew. Ensure that our builds
+		# pick up the Homebrew one by prepending it to our PATH as the
+		# asdf one breaks tests.
+		export PATH="$(brew --prefix)/bin:$PATH"
+
+		CI_OS_NAME=osx
+		;;
 	alpine:*|fedora:*|ubuntu:*)
 		CI_OS_NAME=linux;;
 	*)
@@ -344,6 +351,9 @@
 	then
 		MAKEFLAGS="$MAKEFLAGS APPLE_COMMON_CRYPTO_SHA1=Yes"
 	fi
+
+	P4_PATH="$HOME/custom/p4"
+	export PATH="$P4_PATH:$PATH"
 	;;
 esac
 
diff --git a/ci/print-test-failures.sh b/ci/print-test-failures.sh
index c33ad4e..b1f80ae 100755
--- a/ci/print-test-failures.sh
+++ b/ci/print-test-failures.sh
@@ -8,7 +8,7 @@
 # Tracing executed commands would produce too much noise in the loop below.
 set +x
 
-cd t/
+cd "${TEST_OUTPUT_DIRECTORY:-t/}"
 
 if ! ls test-results/*.exit >/dev/null 2>/dev/null
 then
diff --git a/ci/run-build-and-minimal-fuzzers.sh b/ci/run-build-and-minimal-fuzzers.sh
new file mode 100755
index 0000000..8ba486f
--- /dev/null
+++ b/ci/run-build-and-minimal-fuzzers.sh
@@ -0,0 +1,19 @@
+#!/bin/sh
+#
+# Build and test Git's fuzzers
+#
+
+. ${0%/*}/lib.sh
+
+group "Build fuzzers" make \
+	CC=clang \
+	CXX=clang++ \
+	CFLAGS="-fsanitize=fuzzer-no-link,address" \
+	LIB_FUZZING_ENGINE="-fsanitize=fuzzer,address" \
+	fuzz-all
+
+for fuzzer in commit-graph date pack-headers pack-idx ; do
+	begin_group "fuzz-$fuzzer"
+	./oss-fuzz/fuzz-$fuzzer -verbosity=0 -runs=1 || exit 1
+	end_group "fuzz-$fuzzer"
+done
diff --git a/ci/run-build-and-tests.sh b/ci/run-build-and-tests.sh
index 2528f25..7a1466b 100755
--- a/ci/run-build-and-tests.sh
+++ b/ci/run-build-and-tests.sh
@@ -50,6 +50,8 @@
 then
 	group "Run tests" make test ||
 	handle_failed_tests
+	group "Run unit tests" \
+		make DEFAULT_UNIT_TEST_TARGET=unit-tests-prove unit-tests
 fi
 check_unignored_build_artifacts
 
diff --git a/ci/run-test-slice.sh b/ci/run-test-slice.sh
index a3c6795..ae80943 100755
--- a/ci/run-test-slice.sh
+++ b/ci/run-test-slice.sh
@@ -15,4 +15,9 @@
 	tr '\n' ' ')" ||
 handle_failed_tests
 
+# We only have one unit test at the moment, so run it in the first slice
+if [ "$1" == "0" ] ; then
+	group "Run unit tests" make --quiet -C t unit-tests-prove
+fi
+
 check_unignored_build_artifacts
diff --git a/command-list.txt b/command-list.txt
index 54b2a50..c4cd0f3 100644
--- a/command-list.txt
+++ b/command-list.txt
@@ -160,6 +160,7 @@
 git-remote                              ancillarymanipulators           complete
 git-repack                              ancillarymanipulators           complete
 git-replace                             ancillarymanipulators           complete
+git-replay                              plumbingmanipulators
 git-request-pull                        foreignscminterface             complete
 git-rerere                              ancillaryinterrogators
 git-reset                               mainporcelain           history
diff --git a/commit-graph.c b/commit-graph.c
index 37bd10e..45417d7 100644
--- a/commit-graph.c
+++ b/commit-graph.c
@@ -274,68 +274,37 @@ struct commit_graph *load_commit_graph_one_fd_st(struct repository *r,
 	return ret;
 }
 
-static int verify_commit_graph_lite(struct commit_graph *g)
+static int graph_read_oid_fanout(const unsigned char *chunk_start,
+				 size_t chunk_size, void *data)
 {
+	struct commit_graph *g = data;
 	int i;
 
-	/*
-	 * Basic validation shared between parse_commit_graph()
-	 * which'll be called every time the graph is used, and the
-	 * much more expensive verify_commit_graph() used by
-	 * "commit-graph verify".
-	 *
-	 * There should only be very basic checks here to ensure that
-	 * we don't e.g. segfault in fill_commit_in_graph(), but
-	 * because this is a very hot codepath nothing that e.g. loops
-	 * over g->num_commits, or runs a checksum on the commit-graph
-	 * itself.
-	 */
-	if (!g->chunk_oid_fanout) {
-		error("commit-graph is missing the OID Fanout chunk");
-		return 1;
-	}
-	if (!g->chunk_oid_lookup) {
-		error("commit-graph is missing the OID Lookup chunk");
-		return 1;
-	}
-	if (!g->chunk_commit_data) {
-		error("commit-graph is missing the Commit Data chunk");
-		return 1;
-	}
+	if (chunk_size != 256 * sizeof(uint32_t))
+		return error(_("commit-graph oid fanout chunk is wrong size"));
+	g->chunk_oid_fanout = (const uint32_t *)chunk_start;
+	g->num_commits = ntohl(g->chunk_oid_fanout[255]);
 
 	for (i = 0; i < 255; i++) {
 		uint32_t oid_fanout1 = ntohl(g->chunk_oid_fanout[i]);
 		uint32_t oid_fanout2 = ntohl(g->chunk_oid_fanout[i + 1]);
 
 		if (oid_fanout1 > oid_fanout2) {
-			error("commit-graph fanout values out of order");
+			error(_("commit-graph fanout values out of order"));
 			return 1;
 		}
 	}
-	if (ntohl(g->chunk_oid_fanout[255]) != g->num_commits) {
-		error("commit-graph oid table and fanout disagree on size");
-		return 1;
-	}
 
 	return 0;
 }
 
-static int graph_read_oid_fanout(const unsigned char *chunk_start,
-				 size_t chunk_size, void *data)
-{
-	struct commit_graph *g = data;
-	if (chunk_size != 256 * sizeof(uint32_t))
-		return error("commit-graph oid fanout chunk is wrong size");
-	g->chunk_oid_fanout = (const uint32_t *)chunk_start;
-	return 0;
-}
-
 static int graph_read_oid_lookup(const unsigned char *chunk_start,
 				 size_t chunk_size, void *data)
 {
 	struct commit_graph *g = data;
 	g->chunk_oid_lookup = chunk_start;
-	g->num_commits = chunk_size / g->hash_len;
+	if (chunk_size / g->hash_len != g->num_commits)
+		return error(_("commit-graph OID lookup chunk is the wrong size"));
 	return 0;
 }
 
@@ -343,8 +312,8 @@ static int graph_read_commit_data(const unsigned char *chunk_start,
 				  size_t chunk_size, void *data)
 {
 	struct commit_graph *g = data;
-	if (chunk_size != g->num_commits * GRAPH_DATA_WIDTH)
-		return error("commit-graph commit data chunk is wrong size");
+	if (chunk_size / GRAPH_DATA_WIDTH != g->num_commits)
+		return error(_("commit-graph commit data chunk is wrong size"));
 	g->chunk_commit_data = chunk_start;
 	return 0;
 }
@@ -353,8 +322,8 @@ static int graph_read_generation_data(const unsigned char *chunk_start,
 				      size_t chunk_size, void *data)
 {
 	struct commit_graph *g = data;
-	if (chunk_size != g->num_commits * sizeof(uint32_t))
-		return error("commit-graph generations chunk is wrong size");
+	if (chunk_size / sizeof(uint32_t) != g->num_commits)
+		return error(_("commit-graph generations chunk is wrong size"));
 	g->chunk_generation_data = chunk_start;
 	return 0;
 }
@@ -363,8 +332,8 @@ static int graph_read_bloom_index(const unsigned char *chunk_start,
 				  size_t chunk_size, void *data)
 {
 	struct commit_graph *g = data;
-	if (chunk_size != g->num_commits * 4) {
-		warning("commit-graph changed-path index chunk is too small");
+	if (chunk_size / 4 != g->num_commits) {
+		warning(_("commit-graph changed-path index chunk is too small"));
 		return -1;
 	}
 	g->chunk_bloom_indexes = chunk_start;
@@ -378,8 +347,8 @@ static int graph_read_bloom_data(const unsigned char *chunk_start,
 	uint32_t hash_version;
 
 	if (chunk_size < BLOOMDATA_CHUNK_HEADER_SIZE) {
-		warning("ignoring too-small changed-path chunk"
-			" (%"PRIuMAX" < %"PRIuMAX") in commit-graph file",
+		warning(_("ignoring too-small changed-path chunk"
+			" (%"PRIuMAX" < %"PRIuMAX") in commit-graph file"),
 			(uintmax_t)chunk_size,
 			(uintmax_t)BLOOMDATA_CHUNK_HEADER_SIZE);
 		return -1;
@@ -461,9 +430,19 @@ struct commit_graph *parse_commit_graph(struct repo_settings *s,
 				   GRAPH_HEADER_SIZE, graph->num_chunks, 1))
 		goto free_and_return;
 
-	read_chunk(cf, GRAPH_CHUNKID_OIDFANOUT, graph_read_oid_fanout, graph);
-	read_chunk(cf, GRAPH_CHUNKID_OIDLOOKUP, graph_read_oid_lookup, graph);
-	read_chunk(cf, GRAPH_CHUNKID_DATA, graph_read_commit_data, graph);
+	if (read_chunk(cf, GRAPH_CHUNKID_OIDFANOUT, graph_read_oid_fanout, graph)) {
+		error(_("commit-graph required OID fanout chunk missing or corrupted"));
+		goto free_and_return;
+	}
+	if (read_chunk(cf, GRAPH_CHUNKID_OIDLOOKUP, graph_read_oid_lookup, graph)) {
+		error(_("commit-graph required OID lookup chunk missing or corrupted"));
+		goto free_and_return;
+	}
+	if (read_chunk(cf, GRAPH_CHUNKID_DATA, graph_read_commit_data, graph)) {
+		error(_("commit-graph required commit data chunk missing or corrupted"));
+		goto free_and_return;
+	}
+
 	pair_chunk(cf, GRAPH_CHUNKID_EXTRAEDGES, &graph->chunk_extra_edges,
 		   &graph->chunk_extra_edges_size);
 	pair_chunk(cf, GRAPH_CHUNKID_BASE, &graph->chunk_base_graphs,
@@ -498,9 +477,6 @@ struct commit_graph *parse_commit_graph(struct repo_settings *s,
 
 	oidread(&graph->oid, graph->data + graph->data_len - graph->hash_len);
 
-	if (verify_commit_graph_lite(graph))
-		goto free_and_return;
-
 	free_chunkfile(cf);
 	return graph;
 
@@ -628,7 +604,7 @@ int open_commit_graph_chain(const char *chain_file,
 			/* treat empty files the same as missing */
 			errno = ENOENT;
 		} else {
-			warning("commit-graph chain file too small");
+			warning(_("commit-graph chain file too small"));
 			errno = EINVAL;
 		}
 		return 0;
@@ -972,7 +948,7 @@ static int fill_commit_in_graph(struct repository *r,
 	parent_data_pos = edge_value & GRAPH_EDGE_LAST_MASK;
 	do {
 		if (g->chunk_extra_edges_size / sizeof(uint32_t) <= parent_data_pos) {
-			error("commit-graph extra-edges pointer out of bounds");
+			error(_("commit-graph extra-edges pointer out of bounds"));
 			free_commit_list(item->parents);
 			item->parents = NULL;
 			item->object.parsed = 0;
@@ -2643,19 +2619,16 @@ int write_commit_graph(struct object_directory *odb,
 	oid_array_clear(&ctx->oids);
 	clear_topo_level_slab(&topo_levels);
 
-	if (ctx->commit_graph_filenames_after) {
-		for (i = 0; i < ctx->num_commit_graphs_after; i++) {
-			free(ctx->commit_graph_filenames_after[i]);
-			free(ctx->commit_graph_hash_after[i]);
-		}
+	for (i = 0; i < ctx->num_commit_graphs_before; i++)
+		free(ctx->commit_graph_filenames_before[i]);
+	free(ctx->commit_graph_filenames_before);
 
-		for (i = 0; i < ctx->num_commit_graphs_before; i++)
-			free(ctx->commit_graph_filenames_before[i]);
-
-		free(ctx->commit_graph_filenames_after);
-		free(ctx->commit_graph_filenames_before);
-		free(ctx->commit_graph_hash_after);
+	for (i = 0; i < ctx->num_commit_graphs_after; i++) {
+		free(ctx->commit_graph_filenames_after[i]);
+		free(ctx->commit_graph_hash_after[i]);
 	}
+	free(ctx->commit_graph_filenames_after);
+	free(ctx->commit_graph_hash_after);
 
 	free(ctx);
 
@@ -2692,10 +2665,6 @@ static int verify_one_commit_graph(struct repository *r,
 	struct commit *seen_gen_zero = NULL;
 	struct commit *seen_gen_non_zero = NULL;
 
-	verify_commit_graph_error = verify_commit_graph_lite(g);
-	if (verify_commit_graph_error)
-		return verify_commit_graph_error;
-
 	if (!commit_graph_checksum_valid(g)) {
 		graph_report(_("the commit-graph file has incorrect checksum and is likely corrupt"));
 		verify_commit_graph_error = VERIFY_COMMIT_GRAPH_ERROR_HASH;
diff --git a/compat/mingw.c b/compat/mingw.c
index 4bcbccf..320fb99 100644
--- a/compat/mingw.c
+++ b/compat/mingw.c
@@ -2695,6 +2695,30 @@ static PSID get_current_user_sid(void)
 	return result;
 }
 
+static BOOL user_sid_to_user_name(PSID sid, LPSTR *str)
+{
+	SID_NAME_USE pe_use;
+	DWORD len_user = 0, len_domain = 0;
+	BOOL translate_sid_to_user;
+
+	/*
+	 * returns only FALSE, because the string pointers are NULL
+	 */
+	LookupAccountSidA(NULL, sid, NULL, &len_user, NULL, &len_domain,
+			  &pe_use);
+	/*
+	 * Alloc needed space of the strings
+	 */
+	ALLOC_ARRAY((*str), (size_t)len_domain + (size_t)len_user);
+	translate_sid_to_user = LookupAccountSidA(NULL, sid,
+	    (*str) + len_domain, &len_user, *str, &len_domain, &pe_use);
+	if (!translate_sid_to_user)
+		FREE_AND_NULL(*str);
+	else
+		(*str)[len_domain] = '/';
+	return translate_sid_to_user;
+}
+
 static int acls_supported(const char *path)
 {
 	size_t offset = offset_1st_component(path);
@@ -2776,27 +2800,47 @@ int is_path_owned_by_current_sid(const char *path, struct strbuf *report)
 			strbuf_addf(report, "'%s' is on a file system that does "
 				    "not record ownership\n", path);
 		} else if (report) {
-			LPSTR str1, str2, to_free1 = NULL, to_free2 = NULL;
+			LPSTR str1, str2, str3, str4, to_free1 = NULL,
+			    to_free3 = NULL, to_local_free2 = NULL,
+			    to_local_free4 = NULL;
 
-			if (ConvertSidToStringSidA(sid, &str1))
+			if (user_sid_to_user_name(sid, &str1))
 				to_free1 = str1;
 			else
 				str1 = "(inconvertible)";
-
-			if (!current_user_sid)
-				str2 = "(none)";
-			else if (!IsValidSid(current_user_sid))
-				str2 = "(invalid)";
-			else if (ConvertSidToStringSidA(current_user_sid, &str2))
-				to_free2 = str2;
+			if (ConvertSidToStringSidA(sid, &str2))
+				to_local_free2 = str2;
 			else
 				str2 = "(inconvertible)";
+
+			if (!current_user_sid) {
+				str3 = "(none)";
+				str4 = "(none)";
+			}
+			else if (!IsValidSid(current_user_sid)) {
+				str3 = "(invalid)";
+				str4 = "(invalid)";
+			} else {
+				if (user_sid_to_user_name(current_user_sid,
+							  &str3))
+					to_free3 = str3;
+				else
+					str3 = "(inconvertible)";
+				if (ConvertSidToStringSidA(current_user_sid,
+							   &str4))
+					to_local_free4 = str4;
+				else
+					str4 = "(inconvertible)";
+			}
 			strbuf_addf(report,
 				    "'%s' is owned by:\n"
-				    "\t'%s'\nbut the current user is:\n"
-				    "\t'%s'\n", path, str1, str2);
-			LocalFree(to_free1);
-			LocalFree(to_free2);
+				    "\t%s (%s)\nbut the current user is:\n"
+				    "\t%s (%s)\n",
+				    path, str1, str2, str3, str4);
+			free(to_free1);
+			LocalFree(to_local_free2);
+			free(to_free3);
+			LocalFree(to_local_free4);
 		}
 	}
 
diff --git a/config.c b/config.c
index 9ff6ae1..3cfeb3d 100644
--- a/config.c
+++ b/config.c
@@ -95,7 +95,6 @@ static long config_file_ftell(struct config_source *conf)
 	return ftell(conf->u.file);
 }
 
-
 static int config_buf_fgetc(struct config_source *conf)
 {
 	if (conf->u.buf.pos < conf->u.buf.len)
@@ -1988,7 +1987,27 @@ char *git_system_config(void)
 	return system_config;
 }
 
-void git_global_config(char **user_out, char **xdg_out)
+char *git_global_config(void)
+{
+	char *user_config, *xdg_config;
+
+	git_global_config_paths(&user_config, &xdg_config);
+	if (!user_config) {
+		free(xdg_config);
+		return NULL;
+	}
+
+	if (access_or_warn(user_config, R_OK, 0) && xdg_config &&
+	    !access_or_warn(xdg_config, R_OK, 0)) {
+		free(user_config);
+		return xdg_config;
+	} else {
+		free(xdg_config);
+		return user_config;
+	}
+}
+
+void git_global_config_paths(char **user_out, char **xdg_out)
 {
 	char *user_config = xstrdup_or_null(getenv("GIT_CONFIG_GLOBAL"));
 	char *xdg_config = NULL;
@@ -2041,7 +2060,7 @@ static int do_git_config_sequence(const struct config_options *opts,
 							 data, CONFIG_SCOPE_SYSTEM,
 							 NULL);
 
-	git_global_config(&user_config, &xdg_config);
+	git_global_config_paths(&user_config, &xdg_config);
 
 	if (xdg_config && !access_or_die(xdg_config, R_OK, ACCESS_EACCES_OK))
 		ret += git_config_from_file_with_options(fn, xdg_config, data,
@@ -3418,7 +3437,6 @@ int git_config_set_multivar_in_file_gently(const char *config_filename,
 write_err_out:
 	ret = write_error(get_lock_file_path(&lock));
 	goto out_free;
-
 }
 
 void git_config_set_multivar_in_file(const char *config_filename,
diff --git a/config.h b/config.h
index 14f881e..5dba984 100644
--- a/config.h
+++ b/config.h
@@ -382,7 +382,8 @@ int config_error_nonbool(const char *);
 #endif
 
 char *git_system_config(void);
-void git_global_config(char **user, char **xdg);
+char *git_global_config(void);
+void git_global_config_paths(char **user, char **xdg);
 
 int git_config_parse_parameter(const char *, config_fn_t fn, void *data);
 
diff --git a/config.mak.uname b/config.mak.uname
index 3bb03f4..dacc951 100644
--- a/config.mak.uname
+++ b/config.mak.uname
@@ -158,6 +158,19 @@
 		ifeq ($(shell test -x /usr/local/opt/gettext/bin/msgfmt && echo y),y)
 			MSGFMT = /usr/local/opt/gettext/bin/msgfmt
 		endif
+	# On newer ARM-based machines the default installation path has changed to
+	# /opt/homebrew. Include it in our search paths so that the user does not
+	# have to configure this manually.
+	#
+	# Note that we do not employ the same workaround as above where we manually
+	# add gettext. The issue was fixed more than three years ago by now, and at
+	# that point there haven't been any ARM-based Macs yet.
+	else ifeq ($(shell test -d /opt/homebrew/ && echo y),y)
+		BASIC_CFLAGS += -I/opt/homebrew/include
+		BASIC_LDFLAGS += -L/opt/homebrew/lib
+		ifeq ($(shell test -x /opt/homebrew/bin/msgfmt && echo y),y)
+			MSGFMT = /opt/homebrew/bin/msgfmt
+		endif
 	endif
 
 	# The builtin FSMonitor on MacOS builds upon Simple-IPC.  Both require
diff --git a/configure.ac b/configure.ac
index 276593c..d1a96da 100644
--- a/configure.ac
+++ b/configure.ac
@@ -94,7 +94,7 @@
 [AC_ARG_WITH([$1],
  [AS_HELP_STRING([--with-$1=VALUE], $3)],
  if test -n "$withval"; then
-  if test "$withval" = "yes" -o "$withval" = "no"; then
+  if test "$withval" = "yes" || test "$withval" = "no"; then
     AC_MSG_WARN([You likely do not want either 'yes' or 'no' as]
 		     [a value for $1 ($2).  Maybe you do...?])
   fi
diff --git a/contrib/buildsystems/CMakeLists.txt b/contrib/buildsystems/CMakeLists.txt
index 6b819e2..804629c 100644
--- a/contrib/buildsystems/CMakeLists.txt
+++ b/contrib/buildsystems/CMakeLists.txt
@@ -974,6 +974,35 @@
 parse_makefile_for_sources(test-reftable_SOURCES "REFTABLE_TEST_OBJS")
 list(TRANSFORM test-reftable_SOURCES PREPEND "${CMAKE_SOURCE_DIR}/")
 
+#unit-tests
+add_library(unit-test-lib OBJECT ${CMAKE_SOURCE_DIR}/t/unit-tests/test-lib.c)
+
+parse_makefile_for_scripts(unit_test_PROGRAMS "UNIT_TEST_PROGRAMS" "")
+foreach(unit_test ${unit_test_PROGRAMS})
+	add_executable("${unit_test}" "${CMAKE_SOURCE_DIR}/t/unit-tests/${unit_test}.c")
+	target_link_libraries("${unit_test}" unit-test-lib common-main)
+	set_target_properties("${unit_test}"
+		PROPERTIES RUNTIME_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/t/unit-tests/bin)
+	if(MSVC)
+		set_target_properties("${unit_test}"
+			PROPERTIES RUNTIME_OUTPUT_DIRECTORY_DEBUG ${CMAKE_BINARY_DIR}/t/unit-tests/bin)
+		set_target_properties("${unit_test}"
+			PROPERTIES RUNTIME_OUTPUT_DIRECTORY_RELEASE ${CMAKE_BINARY_DIR}/t/unit-tests/bin)
+	endif()
+	list(APPEND PROGRAMS_BUILT "${unit_test}")
+
+	# t-basic intentionally fails tests, to validate the unit-test infrastructure.
+	# Therefore, it should only be run as part of t0080, which verifies that it
+	# fails only in the expected ways.
+	#
+	# All other unit tests should be run.
+	if(NOT ${unit_test} STREQUAL "t-basic")
+		add_test(NAME "t.unit-tests.${unit_test}"
+			COMMAND "./${unit_test}"
+			WORKING_DIRECTORY ${CMAKE_SOURCE_DIR}/t/unit-tests/bin)
+	endif()
+endforeach()
+
 #test-tool
 parse_makefile_for_sources(test-tool_SOURCES "TEST_BUILTINS_OBJS")
 
@@ -1093,17 +1122,18 @@
 	file(COPY ${CMAKE_SOURCE_DIR}/contrib/completion/git-completion.bash DESTINATION ${CMAKE_BINARY_DIR}/contrib/completion/)
 endif()
 
-file(GLOB test_scipts "${CMAKE_SOURCE_DIR}/t/t[0-9]*.sh")
+file(GLOB test_scripts "${CMAKE_SOURCE_DIR}/t/t[0-9]*.sh")
 
 #test
-foreach(tsh ${test_scipts})
-	add_test(NAME ${tsh}
+foreach(tsh ${test_scripts})
+	string(REGEX REPLACE ".*/(.*)\\.sh" "\\1" test_name ${tsh})
+	add_test(NAME "t.suite.${test_name}"
 		COMMAND ${SH_EXE} ${tsh} --no-bin-wrappers --no-chain-lint -vx
 		WORKING_DIRECTORY ${CMAKE_SOURCE_DIR}/t)
 endforeach()
 
 # This test script takes an extremely long time and is known to time out even
 # on fast machines because it requires in excess of one hour to run
-set_tests_properties("${CMAKE_SOURCE_DIR}/t/t7112-reset-submodule.sh" PROPERTIES TIMEOUT 4000)
+set_tests_properties("t.suite.t7112-reset-submodule" PROPERTIES TIMEOUT 4000)
 
 endif()#BUILD_TESTING
diff --git a/contrib/completion/git-completion.bash b/contrib/completion/git-completion.bash
index e21a39b..1a7bc05 100644
--- a/contrib/completion/git-completion.bash
+++ b/contrib/completion/git-completion.bash
@@ -137,6 +137,9 @@
 __git_pseudoref_exists ()
 {
 	local ref=$1
+	local head
+
+	__git_find_repo_path
 
 	# If the reftable is in use, we have to shell out to 'git rev-parse'
 	# to determine whether the ref exists instead of looking directly in
@@ -144,9 +147,8 @@
 	# Bash builtins since executing Git commands are expensive on some
 	# platforms.
 	if __git_eread "$__git_repo_path/HEAD" head; then
-		b="${head#ref: }"
-		if [ "$b" == "refs/heads/.invalid" ]; then
-			__git -C "$__git_repo_path" rev-parse --verify --quiet "$ref" 2>/dev/null
+		if [ "$head" == "ref: refs/heads/.invalid" ]; then
+			__git show-ref --exists "$ref"
 			return $?
 		fi
 	fi
@@ -1481,12 +1483,32 @@
 {
 	__git_has_doubledash && return
 
-	local subcommands="start bad good skip reset visualize replay log run"
-	local subcommand="$(__git_find_on_cmdline "$subcommands")"
+	__git_find_repo_path
+
+	# If a bisection is in progress get the terms being used.
+	local term_bad term_good
+	if [ -f "$__git_repo_path"/BISECT_TERMS ]; then
+		term_bad=$(__git bisect terms --term-bad)
+		term_good=$(__git bisect terms --term-good)
+	fi
+
+	# We will complete any custom terms, but still always complete the
+	# more usual bad/new/good/old because git bisect gives a good error
+	# message if these are given when not in use, and that's better than
+	# silent refusal to complete if the user is confused.
+	#
+	# We want to recognize 'view' but not complete it, because it overlaps
+	# with 'visualize' too much and is just an alias for it.
+	#
+	local completable_subcommands="start bad new $term_bad good old $term_good terms skip reset visualize replay log run help"
+	local all_subcommands="$completable_subcommands view"
+
+	local subcommand="$(__git_find_on_cmdline "$all_subcommands")"
+
 	if [ -z "$subcommand" ]; then
 		__git_find_repo_path
 		if [ -f "$__git_repo_path"/BISECT_START ]; then
-			__gitcomp "$subcommands"
+			__gitcomp "$completable_subcommands"
 		else
 			__gitcomp "replay start"
 		fi
@@ -1494,7 +1516,26 @@
 	fi
 
 	case "$subcommand" in
-	bad|good|reset|skip|start)
+	start)
+		case "$cur" in
+		--*)
+			__gitcomp "--first-parent --no-checkout --term-new --term-bad --term-old --term-good"
+			return
+			;;
+		*)
+			__git_complete_refs
+			;;
+		esac
+		;;
+	terms)
+		__gitcomp "--term-good --term-old --term-bad --term-new"
+		return
+		;;
+	visualize|view)
+		__git_complete_log_opts
+		return
+		;;
+	bad|new|"$term_bad"|good|old|"$term_good"|reset|skip)
 		__git_complete_refs
 		;;
 	*)
@@ -1656,7 +1697,6 @@
 
 _git_cherry_pick ()
 {
-	__git_find_repo_path
 	if __git_pseudoref_exists CHERRY_PICK_HEAD; then
 		__gitcomp "$__git_cherry_pick_inprogress_options"
 		return
@@ -1807,7 +1847,7 @@
 			--output= --output-indicator-context=
 			--output-indicator-new= --output-indicator-old=
 			--ws-error-highlight=
-			--pickaxe-all --pickaxe-regex
+			--pickaxe-all --pickaxe-regex --patch-with-raw
 "
 
 # Options for diff/difftool
@@ -2071,6 +2111,16 @@
 	--min-age= --until= --before=
 	--min-parents= --max-parents=
 	--no-min-parents --no-max-parents
+	--alternate-refs --ancestry-path
+	--author-date-order --basic-regexp
+	--bisect --boundary --exclude-first-parent-only
+	--exclude-hidden --extended-regexp
+	--fixed-strings --grep-reflog
+	--ignore-missing --left-only --perl-regexp
+	--reflog --regexp-ignore-case --remove-empty
+	--right-only --show-linear-break
+	--show-notes-by-default --show-pulls
+	--since-as-filter --single-worktree
 "
 # Options that go well for log and gitk (not shortlog)
 __git_log_gitk_options="
@@ -2086,6 +2136,7 @@
 # Options accepted by log and show
 __git_log_show_options="
 	--diff-merges --diff-merges= --no-diff-merges --dd --remerge-diff
+	--encoding=
 "
 
 __git_diff_merges_opts="off none on first-parent 1 separate m combined c dense-combined cc remerge r"
@@ -2093,10 +2144,12 @@
 __git_log_pretty_formats="oneline short medium full fuller reference email raw format: tformat: mboxrd"
 __git_log_date_formats="relative iso8601 iso8601-strict rfc2822 short local default human raw unix auto: format:"
 
-_git_log ()
+# Complete porcelain (i.e. not git-rev-list) options and at least some
+# option arguments accepted by git-log.  Note that this same set of options
+# are also accepted by some other git commands besides git-log.
+__git_complete_log_opts ()
 {
-	__git_has_doubledash && return
-	__git_find_repo_path
+	COMPREPLY=()
 
 	local merge=""
 	if __git_pseudoref_exists MERGE_HEAD; then
@@ -2169,6 +2222,8 @@
 			--no-walk --no-walk= --do-walk
 			--parents --children
 			--expand-tabs --expand-tabs= --no-expand-tabs
+			--clear-decorations --decorate-refs=
+			--decorate-refs-exclude=
 			$merge
 			$__git_diff_common_options
 			"
@@ -2190,6 +2245,16 @@
 		return
 		;;
 	esac
+}
+
+_git_log ()
+{
+	__git_has_doubledash && return
+	__git_find_repo_path
+
+	__git_complete_log_opts
+        [ ${#COMPREPLY[@]} -eq 0 ] || return
+
 	__git_complete_revlist
 }
 
@@ -2966,7 +3031,6 @@
 
 _git_restore ()
 {
-	__git_find_repo_path
 	case "$prev" in
 	-s)
 		__git_complete_refs
@@ -2995,7 +3059,6 @@
 
 _git_revert ()
 {
-	__git_find_repo_path
 	if __git_pseudoref_exists REVERT_HEAD; then
 		__gitcomp "$__git_revert_inprogress_options"
 		return
@@ -3117,12 +3180,119 @@
 			COMPREPLY+=("$c/")
 			_found=1
 		fi
-	done < <(git ls-tree -z -d --name-only HEAD $_tmp_dir)
+	done < <(__git ls-tree -z -d --name-only HEAD $_tmp_dir)
 
 	if [[ $_found == 0 ]] && [[ "$cur" =~ /$ ]]; then
 		# No possible further completions any deeper, so assume we're at
 		# a leaf directory and just consider it complete
 		__gitcomp_direct_append "$cur "
+	elif [[ $_found == 0 ]]; then
+		# No possible completions found.  Avoid falling back to
+		# bash's default file and directory completion, because all
+		# valid completions have already been searched and the
+		# fallbacks can do nothing but mislead.  In fact, they can
+		# mislead in three different ways:
+		#    1) Fallback file completion makes no sense when asking
+		#       for directory completions, as this function does.
+		#    2) Fallback directory completion is bad because
+		#       e.g. "/pro" is invalid and should NOT complete to
+		#       "/proc".
+		#    3) Fallback file/directory completion only completes
+		#       on paths that exist in the current working tree,
+		#       i.e. which are *already* part of their
+		#       sparse-checkout.  Thus, normal file and directory
+		#       completion is always useless for "git
+		#       sparse-checkout add" and is also probelmatic for
+		#       "git sparse-checkout set" unless using it to
+		#       strictly narrow the checkout.
+		COMPREPLY=( "" )
+	fi
+}
+
+# In non-cone mode, the arguments to {set,add} are supposed to be
+# patterns, relative to the toplevel directory.  These can be any kind
+# of general pattern, like 'subdir/*.c' and we can't complete on all
+# of those.  However, if the user presses Tab to get tab completion, we
+# presume that they are trying to provide a pattern that names a specific
+# path.
+__gitcomp_slash_leading_paths ()
+{
+	local dequoted_word pfx="" cur_ toplevel
+
+	# Since we are dealing with a sparse-checkout, subdirectories may not
+	# exist in the local working copy.  Therefore, we want to run all
+	# ls-files commands relative to the repository toplevel.
+	toplevel="$(git rev-parse --show-toplevel)/"
+
+	__git_dequote "$cur"
+
+	# If the paths provided by the user already start with '/', then
+	# they are considered relative to the toplevel of the repository
+	# already.  If they do not start with /, then we need to adjust
+	# them to start with the appropriate prefix.
+	case "$cur" in
+	/*)
+		cur="${cur:1}"
+		;;
+	*)
+		pfx="$(__git rev-parse --show-prefix)"
+	esac
+
+	# Since sparse-index is limited to cone-mode, in non-cone-mode the
+	# list of valid paths is precisely the cached files in the index.
+	#
+	# NEEDSWORK:
+	#   1) We probably need to take care of cases where ls-files
+	#      responds with special quoting.
+	#   2) We probably need to take care of cases where ${cur} has
+	#      some kind of special quoting.
+	#   3) On top of any quoting from 1 & 2, we have to provide an extra
+	#      level of quoting for any paths that contain a '*', '?', '\',
+	#      '[', ']', or leading '#' or '!' since those will be
+	#      interpreted by sparse-checkout as something other than a
+	#      literal path character.
+	# Since there are two types of quoting here, this might get really
+	# complex.  For now, just punt on all of this...
+	completions="$(__git -C "${toplevel}" -c core.quotePath=false \
+			 ls-files --cached -- "${pfx}${cur}*" \
+			 | sed -e s%^%/% -e 's%$% %')"
+	# Note, above, though that we needed all of the completions to be
+	# prefixed with a '/', and we want to add a space so that bash
+	# completion will actually complete an entry and let us move on to
+	# the next one.
+
+	# Return what we've found.
+	if test -n "$completions"; then
+		# We found some completions; return them
+		local IFS=$'\n'
+		COMPREPLY=($completions)
+	else
+		# Do NOT fall back to bash-style all-local-files-and-dirs
+		# when we find no match.  Such options are worse than
+		# useless:
+		#     1. "git sparse-checkout add" needs paths that are NOT
+		#        currently in the working copy.  "git
+		#        sparse-checkout set" does as well, except in the
+		#        special cases when users are only trying to narrow
+		#        their sparse checkout to a subset of what they
+		#        already have.
+		#
+		#     2. A path like '.config' is ambiguous as to whether
+		#        the user wants all '.config' files throughout the
+		#        tree, or just the one under the current directory.
+		#        It would result in a warning from the
+		#        sparse-checkout command due to this.  As such, all
+		#        completions of paths should be prefixed with a
+		#        '/'.
+		#
+		#     3. We don't want paths prefixed with a '/' to
+		#        complete files in the system root directory, we
+		#        want it to complete on files relative to the
+		#        repository root.
+		#
+		# As such, make sure that NO completions are offered rather
+		# than falling back to bash's default completions.
+		COMPREPLY=( "" )
 	fi
 }
 
@@ -3130,6 +3300,7 @@
 {
 	local subcommands="list init set disable add reapply"
 	local subcommand="$(__git_find_on_cmdline "$subcommands")"
+	local using_cone=true
 	if [ -z "$subcommand" ]; then
 		__gitcomp "$subcommands"
 		return
@@ -3140,9 +3311,18 @@
 		__gitcomp_builtin sparse-checkout_$subcommand "" "--"
 		;;
 	set,*|add,*)
-		if [ "$(__git config core.sparseCheckoutCone)" == "true" ] ||
-		[ -n "$(__git_find_on_cmdline --cone)" ]; then
+		if [[ "$(__git config core.sparseCheckout)" == "true" &&
+		      "$(__git config core.sparseCheckoutCone)" == "false" &&
+		      -z "$(__git_find_on_cmdline --cone)" ]]; then
+			using_cone=false
+		fi
+		if [[ -n "$(__git_find_on_cmdline --no-cone)" ]]; then
+			using_cone=false
+		fi
+		if [[ "$using_cone" == "true" ]]; then
 			__gitcomp_directories
+		else
+			 __gitcomp_slash_leading_paths
 		fi
 	esac
 }
diff --git a/contrib/completion/git-prompt.sh b/contrib/completion/git-prompt.sh
index 2c03005..71f179c 100644
--- a/contrib/completion/git-prompt.sh
+++ b/contrib/completion/git-prompt.sh
@@ -408,7 +408,7 @@
 
 	local repo_info rev_parse_exit_code
 	repo_info="$(git rev-parse --git-dir --is-inside-git-dir \
-		--is-bare-repository --is-inside-work-tree \
+		--is-bare-repository --is-inside-work-tree --show-ref-format \
 		--short HEAD 2>/dev/null)"
 	rev_parse_exit_code="$?"
 
@@ -421,6 +421,8 @@
 		short_sha="${repo_info##*$'\n'}"
 		repo_info="${repo_info%$'\n'*}"
 	fi
+	local ref_format="${repo_info##*$'\n'}"
+	repo_info="${repo_info%$'\n'*}"
 	local inside_worktree="${repo_info##*$'\n'}"
 	repo_info="${repo_info%$'\n'*}"
 	local bare_repo="${repo_info##*$'\n'}"
@@ -479,12 +481,25 @@
 			b="$(git symbolic-ref HEAD 2>/dev/null)"
 		else
 			local head=""
-			if ! __git_eread "$g/HEAD" head; then
-				return $exit
-			fi
-			# is it a symbolic ref?
-			b="${head#ref: }"
-			if [ "$head" = "$b" ]; then
+
+			case "$ref_format" in
+			files)
+				if ! __git_eread "$g/HEAD" head; then
+					return $exit
+				fi
+
+				if [[ $head == "ref: "* ]]; then
+					head="${head#ref: }"
+				else
+					head=""
+				fi
+				;;
+			*)
+				head="$(git symbolic-ref HEAD 2>/dev/null)"
+				;;
+			esac
+
+			if test -z "$head"; then
 				detached=yes
 				b="$(
 				case "${GIT_PS1_DESCRIBE_STYLE-}" in
@@ -502,6 +517,8 @@
 
 				b="$short_sha..."
 				b="($b)"
+			else
+				b="$head"
 			fi
 		fi
 	fi
diff --git a/contrib/credential/wincred/git-credential-wincred.c b/contrib/credential/wincred/git-credential-wincred.c
index 4cd56c4..4be0d58 100644
--- a/contrib/credential/wincred/git-credential-wincred.c
+++ b/contrib/credential/wincred/git-credential-wincred.c
@@ -35,7 +35,7 @@ static void *xmalloc(size_t size)
 }
 
 static WCHAR *wusername, *password, *protocol, *host, *path, target[1024],
-	*password_expiry_utc;
+	*password_expiry_utc, *oauth_refresh_token;
 
 static void write_item(const char *what, LPCWSTR wbuf, int wlen)
 {
@@ -140,6 +140,11 @@ static void get_credential(void)
 	DWORD num_creds;
 	int i;
 	CREDENTIAL_ATTRIBUTEW *attr;
+	WCHAR *secret;
+	WCHAR *line;
+	WCHAR *remaining_lines;
+	WCHAR *part;
+	WCHAR *remaining_parts;
 
 	if (!CredEnumerateW(L"git:*", 0, &num_creds, &creds))
 		return;
@@ -149,9 +154,24 @@ static void get_credential(void)
 		if (match_cred(creds[i], 0)) {
 			write_item("username", creds[i]->UserName,
 				creds[i]->UserName ? wcslen(creds[i]->UserName) : 0);
-			write_item("password",
-				(LPCWSTR)creds[i]->CredentialBlob,
-				creds[i]->CredentialBlobSize / sizeof(WCHAR));
+			if (creds[i]->CredentialBlobSize > 0) {
+				secret = xmalloc(creds[i]->CredentialBlobSize);
+				wcsncpy_s(secret, creds[i]->CredentialBlobSize, (LPCWSTR)creds[i]->CredentialBlob, creds[i]->CredentialBlobSize / sizeof(WCHAR));
+				line = wcstok_s(secret, L"\r\n", &remaining_lines);
+				write_item("password", line, line ? wcslen(line) : 0);
+				while(line != NULL) {
+					part = wcstok_s(line, L"=", &remaining_parts);
+					if (!wcscmp(part, L"oauth_refresh_token")) {
+						write_item("oauth_refresh_token", remaining_parts, remaining_parts ? wcslen(remaining_parts) : 0);
+					}
+					line = wcstok_s(NULL, L"\r\n", &remaining_lines);
+				}
+				free(secret);
+			} else {
+				write_item("password",
+						(LPCWSTR)creds[i]->CredentialBlob,
+						creds[i]->CredentialBlobSize / sizeof(WCHAR));
+			}
 			for (int j = 0; j < creds[i]->AttributeCount; j++) {
 				attr = creds[i]->Attributes + j;
 				if (!wcscmp(attr->Keyword, L"git_password_expiry_utc")) {
@@ -170,16 +190,26 @@ static void store_credential(void)
 {
 	CREDENTIALW cred;
 	CREDENTIAL_ATTRIBUTEW expiry_attr;
+	WCHAR *secret;
+	int wlen;
 
 	if (!wusername || !password)
 		return;
 
+	if (oauth_refresh_token) {
+		wlen = _scwprintf(L"%s\r\noauth_refresh_token=%s", password, oauth_refresh_token);
+		secret = xmalloc(sizeof(WCHAR) * wlen);
+		_snwprintf_s(secret, sizeof(WCHAR) * wlen, wlen, L"%s\r\noauth_refresh_token=%s", password, oauth_refresh_token);
+	} else {
+		secret = _wcsdup(password);
+	}
+
 	cred.Flags = 0;
 	cred.Type = CRED_TYPE_GENERIC;
 	cred.TargetName = target;
 	cred.Comment = L"saved by git-credential-wincred";
-	cred.CredentialBlobSize = (wcslen(password)) * sizeof(WCHAR);
-	cred.CredentialBlob = (LPVOID)password;
+	cred.CredentialBlobSize = wcslen(secret) * sizeof(WCHAR);
+	cred.CredentialBlob = (LPVOID)_wcsdup(secret);
 	cred.Persist = CRED_PERSIST_LOCAL_MACHINE;
 	cred.AttributeCount = 0;
 	cred.Attributes = NULL;
@@ -194,6 +224,8 @@ static void store_credential(void)
 	cred.TargetAlias = NULL;
 	cred.UserName = wusername;
 
+	free(secret);
+
 	if (!CredWriteW(&cred, 0))
 		die("CredWrite failed");
 }
@@ -265,6 +297,8 @@ static void read_credential(void)
 			password = utf8_to_utf16_dup(v);
 		else if (!strcmp(buf, "password_expiry_utc"))
 			password_expiry_utc = utf8_to_utf16_dup(v);
+		else if (!strcmp(buf, "oauth_refresh_token"))
+			oauth_refresh_token = utf8_to_utf16_dup(v);
 		/*
 		 * Ignore other lines; we don't know what they mean, but
 		 * this future-proofs us when later versions of git do
diff --git a/contrib/subtree/git-subtree.sh b/contrib/subtree/git-subtree.sh
index e0c5d3b..5dab3f5 100755
--- a/contrib/subtree/git-subtree.sh
+++ b/contrib/subtree/git-subtree.sh
@@ -373,7 +373,8 @@
 
 # Usage: process_subtree_split_trailer SPLIT_HASH MAIN_HASH [REPOSITORY]
 process_subtree_split_trailer () {
-	assert test $# = 2 -o $# = 3
+	assert test $# -ge 2
+	assert test $# -le 3
 	b="$1"
 	sq="$2"
 	repository=""
@@ -402,7 +403,8 @@
 
 # Usage: find_latest_squash DIR [REPOSITORY]
 find_latest_squash () {
-	assert test $# = 1 -o $# = 2
+	assert test $# -ge 1
+	assert test $# -le 2
 	dir="$1"
 	repository=""
 	if test "$#" = 2
@@ -455,7 +457,8 @@
 
 # Usage: find_existing_splits DIR REV [REPOSITORY]
 find_existing_splits () {
-	assert test $# = 2 -o $# = 3
+	assert test $# -ge 2
+	assert test $# -le 3
 	debug "Looking for prior splits..."
 	local indent=$(($indent + 1))
 
@@ -489,13 +492,13 @@
 			;;
 		END)
 			debug "Main is: '$main'"
-			if test -z "$main" -a -n "$sub"
+			if test -z "$main" && test -n "$sub"
 			then
 				# squash commits refer to a subtree
 				debug "  Squash: $sq from $sub"
 				cache_set "$sq" "$sub"
 			fi
-			if test -n "$main" -a -n "$sub"
+			if test -n "$main" && test -n "$sub"
 			then
 				debug "  Prior: $main -> $sub"
 				cache_set $main $sub
@@ -638,10 +641,16 @@
 	while read mode type tree name
 	do
 		assert test "$name" = "$dir"
-		assert test "$type" = "tree" -o "$type" = "commit"
-		test "$type" = "commit" && continue  # ignore submodules
-		echo $tree
-		break
+
+		case "$type" in
+		commit)
+			continue;; # ignore submodules
+		tree)
+			echo $tree
+			break;;
+		*)
+			die "fatal: tree entry is of type ${type}, expected tree or commit";;
+		esac
 	done || exit $?
 }
 
@@ -778,6 +787,22 @@
 		die "fatal: '$1' does not look like a ref"
 }
 
+# Usage: check if a commit from another subtree should be
+# ignored from processing for splits
+should_ignore_subtree_split_commit () {
+	assert test $# = 1
+	local rev="$1"
+	if test -n "$(git log -1 --grep="git-subtree-dir:" $rev)"
+	then
+		if test -z "$(git log -1 --grep="git-subtree-mainline:" $rev)" &&
+			test -z "$(git log -1 --grep="git-subtree-dir: $arg_prefix$" $rev)"
+		then
+			return 0
+		fi
+	fi
+	return 1
+}
+
 # Usage: process_split_commit REV PARENTS
 process_split_commit () {
 	assert test $# = 2
@@ -916,7 +941,7 @@
 	if test $# -eq 0
 	then
 		rev=$(git rev-parse HEAD)
-	elif test $# -eq 1 -o $# -eq 2
+	elif test $# -eq 1 || test $# -eq 2
 	then
 		rev=$(git rev-parse -q --verify "$1^{commit}") ||
 			die "fatal: '$1' does not refer to a commit"
@@ -963,7 +988,19 @@
 	eval "$grl" |
 	while read rev parents
 	do
-		process_split_commit "$rev" "$parents"
+		if should_ignore_subtree_split_commit "$rev"
+		then
+			continue
+		fi
+		parsedparents=''
+		for parent in $parents
+		do
+			if ! should_ignore_subtree_split_commit "$parent"
+			then
+				parsedparents="$parsedparents$parent "
+			fi
+		done
+		process_split_commit "$rev" "$parsedparents"
 	done || exit $?
 
 	latest_new=$(cache_get latest_new) || exit $?
@@ -1006,8 +1043,11 @@
 
 # Usage: cmd_merge REV [REPOSITORY]
 cmd_merge () {
-	test $# -eq 1 -o $# -eq 2 ||
+	if test $# -lt 1 || test $# -gt 2
+	then
 		die "fatal: you must provide exactly one revision, and optionally a repository. Got: '$*'"
+	fi
+
 	rev=$(git rev-parse -q --verify "$1^{commit}") ||
 		die "fatal: '$1' does not refer to a commit"
 	repository=""
diff --git a/contrib/subtree/t/t7900-subtree.sh b/contrib/subtree/t/t7900-subtree.sh
index 49a21dd..ca4df5b 100755
--- a/contrib/subtree/t/t7900-subtree.sh
+++ b/contrib/subtree/t/t7900-subtree.sh
@@ -385,6 +385,46 @@
 	)
 '
 
+# Tests that commits from other subtrees are not processed as
+# part of a split.
+#
+# This test performs the following:
+# - Creates Repo with subtrees 'subA' and 'subB'
+# - Creates commits in the repo including changes to subtrees
+# - Runs the following 'split' and commit' commands in order:
+# 	- Perform 'split' on subtree A
+# 	- Perform 'split' on subtree B
+# 	- Create new commits with changes to subtree A and B
+# 	- Perform split on subtree A
+# 	- Check that the commits in subtree B are not processed
+#			as part of the subtree A split
+test_expect_success 'split with multiple subtrees' '
+	subtree_test_create_repo "$test_count" &&
+	subtree_test_create_repo "$test_count/subA" &&
+	subtree_test_create_repo "$test_count/subB" &&
+	test_create_commit "$test_count" main1 &&
+	test_create_commit "$test_count/subA" subA1 &&
+	test_create_commit "$test_count/subA" subA2 &&
+	test_create_commit "$test_count/subA" subA3 &&
+	test_create_commit "$test_count/subB" subB1 &&
+	git -C "$test_count" fetch ./subA HEAD &&
+	git -C "$test_count" subtree add --prefix=subADir FETCH_HEAD &&
+	git -C "$test_count" fetch ./subB HEAD &&
+	git -C "$test_count" subtree add --prefix=subBDir FETCH_HEAD &&
+	test_create_commit "$test_count" subADir/main-subA1 &&
+	test_create_commit "$test_count" subBDir/main-subB1 &&
+	git -C "$test_count" subtree split --prefix=subADir \
+		--squash --rejoin -m "Sub A Split 1" &&
+	git -C "$test_count" subtree split --prefix=subBDir \
+		--squash --rejoin -m "Sub B Split 1" &&
+	test_create_commit "$test_count" subADir/main-subA2 &&
+	test_create_commit "$test_count" subBDir/main-subB2 &&
+	git -C "$test_count" subtree split --prefix=subADir \
+		--squash --rejoin -m "Sub A Split 2" &&
+	test "$(git -C "$test_count" subtree split --prefix=subBDir \
+		--squash --rejoin -d -m "Sub B Split 1" 2>&1 | grep -w "\[1\]")" = ""
+'
+
 test_expect_success 'split sub dir/ with --rejoin from scratch' '
 	subtree_test_create_repo "$test_count" &&
 	test_create_commit "$test_count" main1 &&
diff --git a/diff-lib.c b/diff-lib.c
index 8fde93d..6c8df04 100644
--- a/diff-lib.c
+++ b/diff-lib.c
@@ -37,7 +37,13 @@
  */
 static int check_removed(const struct cache_entry *ce, struct stat *st)
 {
-	if (lstat(ce->name, st) < 0) {
+	int stat_err;
+
+	if (!(ce->ce_flags & CE_FSMONITOR_VALID))
+		stat_err = lstat(ce->name, st);
+	else
+		stat_err = fake_lstat(ce, st);
+	if (stat_err < 0) {
 		if (!is_missing_file_error(errno))
 			return -1;
 		return 1;
diff --git a/dir.c b/dir.c
index 3e75c12..ac69954 100644
--- a/dir.c
+++ b/dir.c
@@ -2178,7 +2178,8 @@ static int exclude_matches_pathspec(const char *path, int pathlen,
 		       PATHSPEC_LITERAL |
 		       PATHSPEC_GLOB |
 		       PATHSPEC_ICASE |
-		       PATHSPEC_EXCLUDE);
+		       PATHSPEC_EXCLUDE |
+		       PATHSPEC_ATTR);
 
 	for (i = 0; i < pathspec->nr; i++) {
 		const struct pathspec_item *item = &pathspec->items[i];
diff --git a/ewah/bitmap.c b/ewah/bitmap.c
index 7b525b1..ac7e0af 100644
--- a/ewah/bitmap.c
+++ b/ewah/bitmap.c
@@ -169,6 +169,15 @@ size_t bitmap_popcount(struct bitmap *self)
 	return count;
 }
 
+int bitmap_is_empty(struct bitmap *self)
+{
+	size_t i;
+	for (i = 0; i < self->word_alloc; i++)
+		if (self->words[i])
+			return 0;
+	return 1;
+}
+
 int bitmap_equals(struct bitmap *self, struct bitmap *other)
 {
 	struct bitmap *big, *small;
diff --git a/ewah/ewok.h b/ewah/ewok.h
index 7eb8b9b..c11d76c 100644
--- a/ewah/ewok.h
+++ b/ewah/ewok.h
@@ -189,5 +189,6 @@ void bitmap_or_ewah(struct bitmap *self, struct ewah_bitmap *other);
 void bitmap_or(struct bitmap *self, const struct bitmap *other);
 
 size_t bitmap_popcount(struct bitmap *self);
+int bitmap_is_empty(struct bitmap *self);
 
 #endif
diff --git a/fsck.c b/fsck.c
index 1ad02fc..8ded0a4 100644
--- a/fsck.c
+++ b/fsck.c
@@ -20,7 +20,6 @@
 #include "packfile.h"
 #include "submodule-config.h"
 #include "config.h"
-#include "credential.h"
 #include "help.h"
 
 static ssize_t max_tree_entry_len = 4096;
@@ -1047,138 +1046,6 @@ int fsck_tag_standalone(const struct object_id *oid, const char *buffer,
 	return ret;
 }
 
-static int starts_with_dot_slash(const char *const path)
-{
-	return path_match_flags(path, PATH_MATCH_STARTS_WITH_DOT_SLASH |
-				PATH_MATCH_XPLATFORM);
-}
-
-static int starts_with_dot_dot_slash(const char *const path)
-{
-	return path_match_flags(path, PATH_MATCH_STARTS_WITH_DOT_DOT_SLASH |
-				PATH_MATCH_XPLATFORM);
-}
-
-static int submodule_url_is_relative(const char *url)
-{
-	return starts_with_dot_slash(url) || starts_with_dot_dot_slash(url);
-}
-
-/*
- * Count directory components that a relative submodule URL should chop
- * from the remote_url it is to be resolved against.
- *
- * In other words, this counts "../" components at the start of a
- * submodule URL.
- *
- * Returns the number of directory components to chop and writes a
- * pointer to the next character of url after all leading "./" and
- * "../" components to out.
- */
-static int count_leading_dotdots(const char *url, const char **out)
-{
-	int result = 0;
-	while (1) {
-		if (starts_with_dot_dot_slash(url)) {
-			result++;
-			url += strlen("../");
-			continue;
-		}
-		if (starts_with_dot_slash(url)) {
-			url += strlen("./");
-			continue;
-		}
-		*out = url;
-		return result;
-	}
-}
-/*
- * Check whether a transport is implemented by git-remote-curl.
- *
- * If it is, returns 1 and writes the URL that would be passed to
- * git-remote-curl to the "out" parameter.
- *
- * Otherwise, returns 0 and leaves "out" untouched.
- *
- * Examples:
- *   http::https://example.com/repo.git -> 1, https://example.com/repo.git
- *   https://example.com/repo.git -> 1, https://example.com/repo.git
- *   git://example.com/repo.git -> 0
- *
- * This is for use in checking for previously exploitable bugs that
- * required a submodule URL to be passed to git-remote-curl.
- */
-static int url_to_curl_url(const char *url, const char **out)
-{
-	/*
-	 * We don't need to check for case-aliases, "http.exe", and so
-	 * on because in the default configuration, is_transport_allowed
-	 * prevents URLs with those schemes from being cloned
-	 * automatically.
-	 */
-	if (skip_prefix(url, "http::", out) ||
-	    skip_prefix(url, "https::", out) ||
-	    skip_prefix(url, "ftp::", out) ||
-	    skip_prefix(url, "ftps::", out))
-		return 1;
-	if (starts_with(url, "http://") ||
-	    starts_with(url, "https://") ||
-	    starts_with(url, "ftp://") ||
-	    starts_with(url, "ftps://")) {
-		*out = url;
-		return 1;
-	}
-	return 0;
-}
-
-static int check_submodule_url(const char *url)
-{
-	const char *curl_url;
-
-	if (looks_like_command_line_option(url))
-		return -1;
-
-	if (submodule_url_is_relative(url) || starts_with(url, "git://")) {
-		char *decoded;
-		const char *next;
-		int has_nl;
-
-		/*
-		 * This could be appended to an http URL and url-decoded;
-		 * check for malicious characters.
-		 */
-		decoded = url_decode(url);
-		has_nl = !!strchr(decoded, '\n');
-
-		free(decoded);
-		if (has_nl)
-			return -1;
-
-		/*
-		 * URLs which escape their root via "../" can overwrite
-		 * the host field and previous components, resolving to
-		 * URLs like https::example.com/submodule.git and
-		 * https:///example.com/submodule.git that were
-		 * susceptible to CVE-2020-11008.
-		 */
-		if (count_leading_dotdots(url, &next) > 0 &&
-		    (*next == ':' || *next == '/'))
-			return -1;
-	}
-
-	else if (url_to_curl_url(url, &curl_url)) {
-		struct credential c = CREDENTIAL_INIT;
-		int ret = 0;
-		if (credential_from_url_gently(&c, curl_url, 1) ||
-		    !*c.host)
-			ret = -1;
-		credential_clear(&c);
-		return ret;
-	}
-
-	return 0;
-}
-
 struct fsck_gitmodules_data {
 	const struct object_id *oid;
 	struct fsck_options *options;
diff --git a/git-compat-util.h b/git-compat-util.h
index 3e7a59b..7c2a653 100644
--- a/git-compat-util.h
+++ b/git-compat-util.h
@@ -225,6 +225,7 @@ struct strbuf;
 #include <stddef.h>
 #include <stdlib.h>
 #include <stdarg.h>
+#include <stdbool.h>
 #include <string.h>
 #ifdef HAVE_STRINGS_H
 #include <strings.h> /* for strcasecmp() */
@@ -684,11 +685,11 @@ report_fn get_warn_routine(void);
 void set_die_is_recursing_routine(int (*routine)(void));
 
 /*
- * If the string "str" begins with the string found in "prefix", return 1.
+ * If the string "str" begins with the string found in "prefix", return true.
  * The "out" parameter is set to "str + strlen(prefix)" (i.e., to the point in
  * the string right after the prefix).
  *
- * Otherwise, return 0 and leave "out" untouched.
+ * Otherwise, return false and leave "out" untouched.
  *
  * Examples:
  *
@@ -699,57 +700,58 @@ void set_die_is_recursing_routine(int (*routine)(void));
  *   [skip prefix if present, otherwise use whole string]
  *   skip_prefix(name, "refs/heads/", &name);
  */
-static inline int skip_prefix(const char *str, const char *prefix,
-			      const char **out)
+static inline bool skip_prefix(const char *str, const char *prefix,
+			       const char **out)
 {
 	do {
 		if (!*prefix) {
 			*out = str;
-			return 1;
+			return true;
 		}
 	} while (*str++ == *prefix++);
-	return 0;
+	return false;
 }
 
 /*
  * Like skip_prefix, but promises never to read past "len" bytes of the input
  * buffer, and returns the remaining number of bytes in "out" via "outlen".
  */
-static inline int skip_prefix_mem(const char *buf, size_t len,
-				  const char *prefix,
-				  const char **out, size_t *outlen)
+static inline bool skip_prefix_mem(const char *buf, size_t len,
+				   const char *prefix,
+				   const char **out, size_t *outlen)
 {
 	size_t prefix_len = strlen(prefix);
 	if (prefix_len <= len && !memcmp(buf, prefix, prefix_len)) {
 		*out = buf + prefix_len;
 		*outlen = len - prefix_len;
-		return 1;
+		return true;
 	}
-	return 0;
+	return false;
 }
 
 /*
- * If buf ends with suffix, return 1 and subtract the length of the suffix
- * from *len. Otherwise, return 0 and leave *len untouched.
+ * If buf ends with suffix, return true and subtract the length of the suffix
+ * from *len. Otherwise, return false and leave *len untouched.
  */
-static inline int strip_suffix_mem(const char *buf, size_t *len,
-				   const char *suffix)
+static inline bool strip_suffix_mem(const char *buf, size_t *len,
+				    const char *suffix)
 {
 	size_t suflen = strlen(suffix);
 	if (*len < suflen || memcmp(buf + (*len - suflen), suffix, suflen))
-		return 0;
+		return false;
 	*len -= suflen;
-	return 1;
+	return true;
 }
 
 /*
- * If str ends with suffix, return 1 and set *len to the size of the string
- * without the suffix. Otherwise, return 0 and set *len to the size of the
+ * If str ends with suffix, return true and set *len to the size of the string
+ * without the suffix. Otherwise, return false and set *len to the size of the
  * string.
  *
  * Note that we do _not_ NUL-terminate str to the new length.
  */
-static inline int strip_suffix(const char *str, const char *suffix, size_t *len)
+static inline bool strip_suffix(const char *str, const char *suffix,
+				size_t *len)
 {
 	*len = strlen(str);
 	return strip_suffix_mem(str, len, suffix);
@@ -1013,6 +1015,15 @@ static inline unsigned long cast_size_t_to_ulong(size_t a)
 	return (unsigned long)a;
 }
 
+static inline uint32_t cast_size_t_to_uint32_t(size_t a)
+{
+	if (a != (uint32_t)a)
+		die("object too large to read on this platform: %"
+		    PRIuMAX" is cut off to %u",
+		    (uintmax_t)a, (uint32_t)a);
+	return (uint32_t)a;
+}
+
 static inline int cast_size_t_to_int(size_t a)
 {
 	if (a > INT_MAX)
diff --git a/git-p4.py b/git-p4.py
index 156597a..28ab12c 100755
--- a/git-p4.py
+++ b/git-p4.py
@@ -4251,7 +4251,8 @@ def run(self, args):
         if self.tempBranches != []:
             for branch in self.tempBranches:
                 read_pipe(["git", "update-ref", "-d", branch])
-            os.rmdir(os.path.join(os.environ.get("GIT_DIR", ".git"), self.tempBranchLocation))
+            if len(read_pipe(["git", "for-each-ref", self.tempBranchLocation])) > 0:
+                   die("There are unexpected temporary branches")
 
         # Create a symbolic ref p4/HEAD pointing to p4/<branch> to allow
         # a convenient shortcut refname "p4".
diff --git a/git.c b/git.c
index c67e44d..7068a18 100644
--- a/git.c
+++ b/git.c
@@ -594,6 +594,7 @@ static struct cmd_struct commands[] = {
 	{ "remote-fd", cmd_remote_fd, NO_PARSEOPT },
 	{ "repack", cmd_repack, RUN_SETUP },
 	{ "replace", cmd_replace, RUN_SETUP },
+	{ "replay", cmd_replay, RUN_SETUP },
 	{ "rerere", cmd_rerere, RUN_SETUP },
 	{ "reset", cmd_reset, RUN_SETUP },
 	{ "restore", cmd_restore, RUN_SETUP | NEED_WORK_TREE },
diff --git a/gitweb/gitweb.perl b/gitweb/gitweb.perl
index fc6d5dd..ccd14e0 100755
--- a/gitweb/gitweb.perl
+++ b/gitweb/gitweb.perl
@@ -728,9 +728,11 @@
 sub read_config_file {
 	my $filename = shift;
 	return unless defined $filename;
-	# die if there are errors parsing config file
 	if (-e $filename) {
 		do $filename;
+		# die if there is a problem accessing the file
+		die $! if $!;
+		# die if there are errors parsing config file
 		die $@ if $@;
 		return 1;
 	}
diff --git a/http-backend.c b/http-backend.c
index ff07b87..1ed1e29 100644
--- a/http-backend.c
+++ b/http-backend.c
@@ -38,6 +38,7 @@ struct rpc_service {
 static struct rpc_service rpc_service[] = {
 	{ "upload-pack", "uploadpack", 1, 1 },
 	{ "receive-pack", "receivepack", 0, -1 },
+	{ "upload-archive", "uploadarchive", 0, -1 },
 };
 
 static struct string_list *get_parameters(void)
@@ -639,10 +640,15 @@ static void check_content_type(struct strbuf *hdr, const char *accepted_type)
 
 static void service_rpc(struct strbuf *hdr, char *service_name)
 {
-	const char *argv[] = {NULL, "--stateless-rpc", ".", NULL};
+	struct strvec argv = STRVEC_INIT;
 	struct rpc_service *svc = select_service(hdr, service_name);
 	struct strbuf buf = STRBUF_INIT;
 
+	strvec_push(&argv, svc->name);
+	if (strcmp(service_name, "git-upload-archive"))
+		strvec_push(&argv, "--stateless-rpc");
+	strvec_push(&argv, ".");
+
 	strbuf_reset(&buf);
 	strbuf_addf(&buf, "application/x-git-%s-request", svc->name);
 	check_content_type(hdr, buf.buf);
@@ -655,9 +661,9 @@ static void service_rpc(struct strbuf *hdr, char *service_name)
 
 	end_headers(hdr);
 
-	argv[0] = svc->name;
-	run_service(argv, svc->buffer_input);
+	run_service(argv.v, svc->buffer_input);
 	strbuf_release(&buf);
+	strvec_clear(&argv);
 }
 
 static int dead;
@@ -723,6 +729,7 @@ static struct service_cmd {
 	{"GET", "/objects/pack/pack-[0-9a-f]{64}\\.idx$", get_idx_file},
 
 	{"POST", "/git-upload-pack$", service_rpc},
+	{"POST", "/git-upload-archive$", service_rpc},
 	{"POST", "/git-receive-pack$", service_rpc}
 };
 
diff --git a/http-push.c b/http-push.c
index b4d0b2a..12d1113 100644
--- a/http-push.c
+++ b/http-push.c
@@ -1851,6 +1851,7 @@ int cmd_main(int argc, const char **argv)
 
 		if (oideq(&ref->old_oid, &ref->peer_ref->new_oid)) {
 			if (push_verbosely)
+				/* stable plumbing output; do not modify or localize */
 				fprintf(stderr, "'%s': up-to-date\n", ref->name);
 			if (helper_status)
 				printf("ok %s up to date\n", ref->name);
@@ -1871,6 +1872,7 @@ int cmd_main(int argc, const char **argv)
 				 * commits at the remote end and likely
 				 * we were not up to date to begin with.
 				 */
+				/* stable plumbing output; do not modify or localize */
 				error("remote '%s' is not an ancestor of\n"
 				      "local '%s'.\n"
 				      "Maybe you are not up-to-date and "
diff --git a/mem-pool.c b/mem-pool.c
index c34846d..c7d6256 100644
--- a/mem-pool.c
+++ b/mem-pool.c
@@ -89,9 +89,7 @@ void *mem_pool_alloc(struct mem_pool *pool, size_t len)
 	struct mp_block *p = NULL;
 	void *r;
 
-	/* round up to a 'GIT_MAX_ALIGNMENT' alignment */
-	if (len & (GIT_MAX_ALIGNMENT - 1))
-		len += GIT_MAX_ALIGNMENT - (len & (GIT_MAX_ALIGNMENT - 1));
+	len = DIV_ROUND_UP(len, GIT_MAX_ALIGNMENT) * GIT_MAX_ALIGNMENT;
 
 	if (pool->mp_block &&
 	    pool->mp_block->end - pool->mp_block->next_free >= len)
@@ -99,9 +97,9 @@ void *mem_pool_alloc(struct mem_pool *pool, size_t len)
 
 	if (!p) {
 		if (len >= (pool->block_alloc / 2))
-			return mem_pool_alloc_block(pool, len, pool->mp_block);
-
-		p = mem_pool_alloc_block(pool, pool->block_alloc, NULL);
+			p = mem_pool_alloc_block(pool, len, pool->mp_block);
+		else
+			p = mem_pool_alloc_block(pool, pool->block_alloc, NULL);
 	}
 
 	r = p->next_free;
diff --git a/merge-ll.c b/merge-ll.c
index 1df58eb..5ffb045 100644
--- a/merge-ll.c
+++ b/merge-ll.c
@@ -185,9 +185,9 @@ static void create_temp(mmfile_t *src, char *path, size_t len)
 static enum ll_merge_result ll_ext_merge(const struct ll_merge_driver *fn,
 			mmbuffer_t *result,
 			const char *path,
-			mmfile_t *orig, const char *orig_name UNUSED,
-			mmfile_t *src1, const char *name1 UNUSED,
-			mmfile_t *src2, const char *name2 UNUSED,
+			mmfile_t *orig, const char *orig_name,
+			mmfile_t *src1, const char *name1,
+			mmfile_t *src2, const char *name2,
 			const struct ll_merge_options *opts,
 			int marker_size)
 {
@@ -222,6 +222,12 @@ static enum ll_merge_result ll_ext_merge(const struct ll_merge_driver *fn,
 			strbuf_addf(&cmd, "%d", marker_size);
 		else if (skip_prefix(format, "P", &format))
 			sq_quote_buf(&cmd, path);
+		else if (skip_prefix(format, "S", &format))
+			sq_quote_buf(&cmd, orig_name ? orig_name : "");
+		else if (skip_prefix(format, "X", &format))
+			sq_quote_buf(&cmd, name1 ? name1 : "");
+		else if (skip_prefix(format, "Y", &format))
+			sq_quote_buf(&cmd, name2 ? name2 : "");
 		else
 			strbuf_addch(&cmd, '%');
 	}
@@ -315,7 +321,12 @@ static int read_merge_config(const char *var, const char *value,
 		 *    %B - temporary file name for the other branches' version.
 		 *    %L - conflict marker length
 		 *    %P - the original path (safely quoted for the shell)
+		 *    %S - the revision for the merge base
+		 *    %X - the revision for our version
+		 *    %Y - the revision for their version
 		 *
+		 * If the file is not named indentically in all versions, then each
+		 * revision is joined with the corresponding path, separated by a colon.
 		 * The external merge driver should write the results in the
 		 * file named by %A, and signal that it has done with zero exit
 		 * status.
diff --git a/merge-ort.c b/merge-ort.c
index cb83449..8617bab 100644
--- a/merge-ort.c
+++ b/merge-ort.c
@@ -38,6 +38,7 @@
 #include "path.h"
 #include "promisor-remote.h"
 #include "read-cache-ll.h"
+#include "refs.h"
 #include "revision.h"
 #include "sparse-index.h"
 #include "strmap.h"
@@ -4659,9 +4660,6 @@ void merge_switch_to_result(struct merge_options *opt,
 {
 	assert(opt->priv == NULL);
 	if (result->clean >= 0 && update_worktree_and_index) {
-		const char *filename;
-		FILE *fp;
-
 		trace2_region_enter("merge", "checkout", opt->repo);
 		if (checkout(opt, head, result->tree)) {
 			/* failure to function */
@@ -4687,10 +4685,17 @@ void merge_switch_to_result(struct merge_options *opt,
 		trace2_region_leave("merge", "record_conflicted", opt->repo);
 
 		trace2_region_enter("merge", "write_auto_merge", opt->repo);
-		filename = git_path_auto_merge(opt->repo);
-		fp = xfopen(filename, "w");
-		fprintf(fp, "%s\n", oid_to_hex(&result->tree->object.oid));
-		fclose(fp);
+		if (refs_update_ref(get_main_ref_store(opt->repo), "", "AUTO_MERGE",
+				    &result->tree->object.oid, NULL, REF_NO_DEREF,
+				    UPDATE_REFS_MSG_ON_ERR)) {
+			/* failure to function */
+			opt->priv = NULL;
+			result->clean = -1;
+			merge_finalize(opt, result);
+			trace2_region_leave("merge", "write_auto_merge",
+					    opt->repo);
+			return;
+		}
 		trace2_region_leave("merge", "write_auto_merge", opt->repo);
 	}
 	if (display_update_msgs)
diff --git a/midx.c b/midx.c
index 2f3863c..85e1c2c 100644
--- a/midx.c
+++ b/midx.c
@@ -21,6 +21,7 @@
 #include "refs.h"
 #include "revision.h"
 #include "list-objects.h"
+#include "pack-revindex.h"
 
 #define MIDX_SIGNATURE 0x4d494458 /* "MIDX" */
 #define MIDX_VERSION 1
@@ -33,6 +34,7 @@
 
 #define MIDX_CHUNK_ALIGNMENT 4
 #define MIDX_CHUNKID_PACKNAMES 0x504e414d /* "PNAM" */
+#define MIDX_CHUNKID_BITMAPPEDPACKS 0x42544d50 /* "BTMP" */
 #define MIDX_CHUNKID_OIDFANOUT 0x4f494446 /* "OIDF" */
 #define MIDX_CHUNKID_OIDLOOKUP 0x4f49444c /* "OIDL" */
 #define MIDX_CHUNKID_OBJECTOFFSETS 0x4f4f4646 /* "OOFF" */
@@ -41,6 +43,7 @@
 #define MIDX_CHUNK_FANOUT_SIZE (sizeof(uint32_t) * 256)
 #define MIDX_CHUNK_OFFSET_WIDTH (2 * sizeof(uint32_t))
 #define MIDX_CHUNK_LARGE_OFFSET_WIDTH (sizeof(uint64_t))
+#define MIDX_CHUNK_BITMAPPED_PACKS_WIDTH (2 * sizeof(uint32_t))
 #define MIDX_LARGE_OFFSET_NEEDED 0x80000000
 
 #define PACK_EXPIRED UINT_MAX
@@ -64,6 +67,7 @@ void get_midx_rev_filename(struct strbuf *out, struct multi_pack_index *m)
 static int midx_read_oid_fanout(const unsigned char *chunk_start,
 				size_t chunk_size, void *data)
 {
+	int i;
 	struct multi_pack_index *m = data;
 	m->chunk_oid_fanout = (uint32_t *)chunk_start;
 
@@ -71,6 +75,16 @@ static int midx_read_oid_fanout(const unsigned char *chunk_start,
 		error(_("multi-pack-index OID fanout is of the wrong size"));
 		return 1;
 	}
+	for (i = 0; i < 255; i++) {
+		uint32_t oid_fanout1 = ntohl(m->chunk_oid_fanout[i]);
+		uint32_t oid_fanout2 = ntohl(m->chunk_oid_fanout[i+1]);
+
+		if (oid_fanout1 > oid_fanout2) {
+			error(_("oid fanout out of order: fanout[%d] = %"PRIx32" > %"PRIx32" = fanout[%d]"),
+			      i, oid_fanout1, oid_fanout2, i + 1);
+			return 1;
+		}
+	}
 	m->num_objects = ntohl(m->chunk_oid_fanout[255]);
 	return 0;
 }
@@ -164,6 +178,8 @@ struct multi_pack_index *load_multi_pack_index(const char *object_dir, int local
 
 	m->num_packs = get_be32(m->data + MIDX_BYTE_NUM_PACKS);
 
+	m->preferred_pack_idx = -1;
+
 	cf = init_chunkfile(NULL);
 
 	if (read_table_of_contents(cf, m->data, midx_size,
@@ -182,6 +198,9 @@ struct multi_pack_index *load_multi_pack_index(const char *object_dir, int local
 
 	pair_chunk(cf, MIDX_CHUNKID_LARGEOFFSETS, &m->chunk_large_offsets,
 		   &m->chunk_large_offsets_len);
+	pair_chunk(cf, MIDX_CHUNKID_BITMAPPEDPACKS,
+		   (const unsigned char **)&m->chunk_bitmapped_packs,
+		   &m->chunk_bitmapped_packs_len);
 
 	if (git_env_bool("GIT_TEST_MIDX_READ_RIDX", 1))
 		pair_chunk(cf, MIDX_CHUNKID_REVINDEX, &m->chunk_revindex,
@@ -275,6 +294,26 @@ int prepare_midx_pack(struct repository *r, struct multi_pack_index *m, uint32_t
 	return 0;
 }
 
+int nth_bitmapped_pack(struct repository *r, struct multi_pack_index *m,
+		       struct bitmapped_pack *bp, uint32_t pack_int_id)
+{
+	if (!m->chunk_bitmapped_packs)
+		return error(_("MIDX does not contain the BTMP chunk"));
+
+	if (prepare_midx_pack(r, m, pack_int_id))
+		return error(_("could not load bitmapped pack %"PRIu32), pack_int_id);
+
+	bp->p = m->packs[pack_int_id];
+	bp->bitmap_pos = get_be32((char *)m->chunk_bitmapped_packs +
+				  MIDX_CHUNK_BITMAPPED_PACKS_WIDTH * pack_int_id);
+	bp->bitmap_nr = get_be32((char *)m->chunk_bitmapped_packs +
+				 MIDX_CHUNK_BITMAPPED_PACKS_WIDTH * pack_int_id +
+				 sizeof(uint32_t));
+	bp->pack_int_id = pack_int_id;
+
+	return 0;
+}
+
 int bsearch_midx(const struct object_id *oid, struct multi_pack_index *m, uint32_t *result)
 {
 	return bsearch_hash(oid->hash, m->chunk_oid_fanout, m->chunk_oid_lookup,
@@ -392,7 +431,8 @@ static int cmp_idx_or_pack_name(const char *idx_or_pack_name,
 	return strcmp(idx_or_pack_name, idx_name);
 }
 
-int midx_contains_pack(struct multi_pack_index *m, const char *idx_or_pack_name)
+int midx_locate_pack(struct multi_pack_index *m, const char *idx_or_pack_name,
+		     uint32_t *pos)
 {
 	uint32_t first = 0, last = m->num_packs;
 
@@ -403,8 +443,11 @@ int midx_contains_pack(struct multi_pack_index *m, const char *idx_or_pack_name)
 
 		current = m->pack_names[mid];
 		cmp = cmp_idx_or_pack_name(idx_or_pack_name, current);
-		if (!cmp)
+		if (!cmp) {
+			if (pos)
+				*pos = mid;
 			return 1;
+		}
 		if (cmp > 0) {
 			first = mid + 1;
 			continue;
@@ -415,6 +458,28 @@ int midx_contains_pack(struct multi_pack_index *m, const char *idx_or_pack_name)
 	return 0;
 }
 
+int midx_contains_pack(struct multi_pack_index *m, const char *idx_or_pack_name)
+{
+	return midx_locate_pack(m, idx_or_pack_name, NULL);
+}
+
+int midx_preferred_pack(struct multi_pack_index *m, uint32_t *pack_int_id)
+{
+	if (m->preferred_pack_idx == -1) {
+		if (load_midx_revindex(m) < 0) {
+			m->preferred_pack_idx = -2;
+			return -1;
+		}
+
+		m->preferred_pack_idx =
+			nth_midxed_pack_int_id(m, pack_pos_to_midx(m, 0));
+	} else if (m->preferred_pack_idx == -2)
+		return -1; /* no revindex */
+
+	*pack_int_id = m->preferred_pack_idx;
+	return 0;
+}
+
 int prepare_multi_pack_index_one(struct repository *r, const char *object_dir, int local)
 {
 	struct multi_pack_index *m;
@@ -457,13 +522,31 @@ static size_t write_midx_header(struct hashfile *f,
 	return MIDX_HEADER_SIZE;
 }
 
+#define BITMAP_POS_UNKNOWN (~((uint32_t)0))
+
 struct pack_info {
 	uint32_t orig_pack_int_id;
 	char *pack_name;
 	struct packed_git *p;
+
+	uint32_t bitmap_pos;
+	uint32_t bitmap_nr;
+
 	unsigned expired : 1;
 };
 
+static void fill_pack_info(struct pack_info *info,
+			   struct packed_git *p, const char *pack_name,
+			   uint32_t orig_pack_int_id)
+{
+	memset(info, 0, sizeof(struct pack_info));
+
+	info->orig_pack_int_id = orig_pack_int_id;
+	info->pack_name = xstrdup(pack_name);
+	info->p = p;
+	info->bitmap_pos = BITMAP_POS_UNKNOWN;
+}
+
 static int pack_info_compare(const void *_a, const void *_b)
 {
 	struct pack_info *a = (struct pack_info *)_a;
@@ -504,6 +587,7 @@ static void add_pack_to_midx(const char *full_path, size_t full_path_len,
 			     const char *file_name, void *data)
 {
 	struct write_midx_context *ctx = data;
+	struct packed_git *p;
 
 	if (ends_with(file_name, ".idx")) {
 		display_progress(ctx->progress, ++ctx->pack_paths_checked);
@@ -530,27 +614,22 @@ static void add_pack_to_midx(const char *full_path, size_t full_path_len,
 
 		ALLOC_GROW(ctx->info, ctx->nr + 1, ctx->alloc);
 
-		ctx->info[ctx->nr].p = add_packed_git(full_path,
-						      full_path_len,
-						      0);
-
-		if (!ctx->info[ctx->nr].p) {
+		p = add_packed_git(full_path, full_path_len, 0);
+		if (!p) {
 			warning(_("failed to add packfile '%s'"),
 				full_path);
 			return;
 		}
 
-		if (open_pack_index(ctx->info[ctx->nr].p)) {
+		if (open_pack_index(p)) {
 			warning(_("failed to open pack-index '%s'"),
 				full_path);
-			close_pack(ctx->info[ctx->nr].p);
-			FREE_AND_NULL(ctx->info[ctx->nr].p);
+			close_pack(p);
+			free(p);
 			return;
 		}
 
-		ctx->info[ctx->nr].pack_name = xstrdup(file_name);
-		ctx->info[ctx->nr].orig_pack_int_id = ctx->nr;
-		ctx->info[ctx->nr].expired = 0;
+		fill_pack_info(&ctx->info[ctx->nr], p, file_name, ctx->nr);
 		ctx->nr++;
 	}
 }
@@ -806,6 +885,26 @@ static int write_midx_pack_names(struct hashfile *f, void *data)
 	return 0;
 }
 
+static int write_midx_bitmapped_packs(struct hashfile *f, void *data)
+{
+	struct write_midx_context *ctx = data;
+	size_t i;
+
+	for (i = 0; i < ctx->nr; i++) {
+		struct pack_info *pack = &ctx->info[i];
+		if (pack->expired)
+			continue;
+
+		if (pack->bitmap_pos == BITMAP_POS_UNKNOWN && pack->bitmap_nr)
+			BUG("pack '%s' has no bitmap position, but has %d bitmapped object(s)",
+			    pack->pack_name, pack->bitmap_nr);
+
+		hashwrite_be32(f, pack->bitmap_pos);
+		hashwrite_be32(f, pack->bitmap_nr);
+	}
+	return 0;
+}
+
 static int write_midx_oid_fanout(struct hashfile *f,
 				 void *data)
 {
@@ -973,8 +1072,19 @@ static uint32_t *midx_pack_order(struct write_midx_context *ctx)
 	QSORT(data, ctx->entries_nr, midx_pack_order_cmp);
 
 	ALLOC_ARRAY(pack_order, ctx->entries_nr);
-	for (i = 0; i < ctx->entries_nr; i++)
+	for (i = 0; i < ctx->entries_nr; i++) {
+		struct pack_midx_entry *e = &ctx->entries[data[i].nr];
+		struct pack_info *pack = &ctx->info[ctx->pack_perm[e->pack_int_id]];
+		if (pack->bitmap_pos == BITMAP_POS_UNKNOWN)
+			pack->bitmap_pos = i;
+		pack->bitmap_nr++;
 		pack_order[i] = data[i].nr;
+	}
+	for (i = 0; i < ctx->nr; i++) {
+		struct pack_info *pack = &ctx->info[ctx->pack_perm[i]];
+		if (pack->bitmap_pos == BITMAP_POS_UNKNOWN)
+			pack->bitmap_pos = 0;
+	}
 	free(data);
 
 	trace2_region_leave("midx", "midx_pack_order", the_repository);
@@ -1275,6 +1385,7 @@ static int write_midx_internal(const char *object_dir,
 	struct hashfile *f = NULL;
 	struct lock_file lk;
 	struct write_midx_context ctx = { 0 };
+	int bitmapped_packs_concat_len = 0;
 	int pack_name_concat_len = 0;
 	int dropped_packs = 0;
 	int result = 0;
@@ -1310,11 +1421,6 @@ static int write_midx_internal(const char *object_dir,
 		for (i = 0; i < ctx.m->num_packs; i++) {
 			ALLOC_GROW(ctx.info, ctx.nr + 1, ctx.alloc);
 
-			ctx.info[ctx.nr].orig_pack_int_id = i;
-			ctx.info[ctx.nr].pack_name = xstrdup(ctx.m->pack_names[i]);
-			ctx.info[ctx.nr].p = ctx.m->packs[i];
-			ctx.info[ctx.nr].expired = 0;
-
 			if (flags & MIDX_WRITE_REV_INDEX) {
 				/*
 				 * If generating a reverse index, need to have
@@ -1330,10 +1436,10 @@ static int write_midx_internal(const char *object_dir,
 				if (open_pack_index(ctx.m->packs[i]))
 					die(_("could not open index for %s"),
 					    ctx.m->packs[i]->pack_name);
-				ctx.info[ctx.nr].p = ctx.m->packs[i];
 			}
 
-			ctx.nr++;
+			fill_pack_info(&ctx.info[ctx.nr++], ctx.m->packs[i],
+				       ctx.m->pack_names[i], i);
 		}
 	}
 
@@ -1492,8 +1598,10 @@ static int write_midx_internal(const char *object_dir,
 	}
 
 	for (i = 0; i < ctx.nr; i++) {
-		if (!ctx.info[i].expired)
-			pack_name_concat_len += strlen(ctx.info[i].pack_name) + 1;
+		if (ctx.info[i].expired)
+			continue;
+		pack_name_concat_len += strlen(ctx.info[i].pack_name) + 1;
+		bitmapped_packs_concat_len += 2 * sizeof(uint32_t);
 	}
 
 	/* Check that the preferred pack wasn't expired (if given). */
@@ -1553,6 +1661,9 @@ static int write_midx_internal(const char *object_dir,
 		add_chunk(cf, MIDX_CHUNKID_REVINDEX,
 			  st_mult(ctx.entries_nr, sizeof(uint32_t)),
 			  write_midx_revindex);
+		add_chunk(cf, MIDX_CHUNKID_BITMAPPEDPACKS,
+			  bitmapped_packs_concat_len,
+			  write_midx_bitmapped_packs);
 	}
 
 	write_midx_header(f, get_num_chunks(cf), ctx.nr - dropped_packs);
@@ -1592,8 +1703,13 @@ static int write_midx_internal(const char *object_dir,
 				      flags) < 0) {
 			error(_("could not write multi-pack bitmap"));
 			result = 1;
+			clear_packing_data(&pdata);
+			free(commits);
 			goto cleanup;
 		}
+
+		clear_packing_data(&pdata);
+		free(commits);
 	}
 	/*
 	 * NOTE: Do not use ctx.entries beyond this point, since it might
@@ -1782,15 +1898,6 @@ int verify_midx_file(struct repository *r, const char *object_dir, unsigned flag
 	}
 	stop_progress(&progress);
 
-	for (i = 0; i < 255; i++) {
-		uint32_t oid_fanout1 = ntohl(m->chunk_oid_fanout[i]);
-		uint32_t oid_fanout2 = ntohl(m->chunk_oid_fanout[i + 1]);
-
-		if (oid_fanout1 > oid_fanout2)
-			midx_report(_("oid fanout out of order: fanout[%d] = %"PRIx32" > %"PRIx32" = fanout[%d]"),
-				    i, oid_fanout1, oid_fanout2, i + 1);
-	}
-
 	if (m->num_objects == 0) {
 		midx_report(_("the midx contains no oid"));
 		/*
diff --git a/midx.h b/midx.h
index eb57a37..b374a7a 100644
--- a/midx.h
+++ b/midx.h
@@ -6,6 +6,7 @@
 struct object_id;
 struct pack_entry;
 struct repository;
+struct bitmapped_pack;
 
 #define GIT_TEST_MULTI_PACK_INDEX "GIT_TEST_MULTI_PACK_INDEX"
 #define GIT_TEST_MULTI_PACK_INDEX_WRITE_BITMAP \
@@ -27,11 +28,14 @@ struct multi_pack_index {
 	unsigned char num_chunks;
 	uint32_t num_packs;
 	uint32_t num_objects;
+	int preferred_pack_idx;
 
 	int local;
 
 	const unsigned char *chunk_pack_names;
 	size_t chunk_pack_names_len;
+	const uint32_t *chunk_bitmapped_packs;
+	size_t chunk_bitmapped_packs_len;
 	const uint32_t *chunk_oid_fanout;
 	const unsigned char *chunk_oid_lookup;
 	const unsigned char *chunk_object_offsets;
@@ -57,6 +61,8 @@ void get_midx_rev_filename(struct strbuf *out, struct multi_pack_index *m);
 
 struct multi_pack_index *load_multi_pack_index(const char *object_dir, int local);
 int prepare_midx_pack(struct repository *r, struct multi_pack_index *m, uint32_t pack_int_id);
+int nth_bitmapped_pack(struct repository *r, struct multi_pack_index *m,
+		       struct bitmapped_pack *bp, uint32_t pack_int_id);
 int bsearch_midx(const struct object_id *oid, struct multi_pack_index *m, uint32_t *result);
 off_t nth_midxed_offset(struct multi_pack_index *m, uint32_t pos);
 uint32_t nth_midxed_pack_int_id(struct multi_pack_index *m, uint32_t pos);
@@ -64,7 +70,11 @@ struct object_id *nth_midxed_object_oid(struct object_id *oid,
 					struct multi_pack_index *m,
 					uint32_t n);
 int fill_midx_entry(struct repository *r, const struct object_id *oid, struct pack_entry *e, struct multi_pack_index *m);
-int midx_contains_pack(struct multi_pack_index *m, const char *idx_or_pack_name);
+int midx_contains_pack(struct multi_pack_index *m,
+		       const char *idx_or_pack_name);
+int midx_locate_pack(struct multi_pack_index *m, const char *idx_or_pack_name,
+		     uint32_t *pos);
+int midx_preferred_pack(struct multi_pack_index *m, uint32_t *pack_int_id);
 int prepare_multi_pack_index_one(struct repository *r, const char *object_dir, int local);
 
 /*
diff --git a/neue b/neue
new file mode 100644
index 0000000..e69de29
--- /dev/null
+++ b/neue
diff --git a/oss-fuzz/.gitignore b/oss-fuzz/.gitignore
index 9acb744..5b95408 100644
--- a/oss-fuzz/.gitignore
+++ b/oss-fuzz/.gitignore
@@ -1,3 +1,4 @@
 fuzz-commit-graph
+fuzz-date
 fuzz-pack-headers
 fuzz-pack-idx
diff --git a/oss-fuzz/dummy-cmd-main.c b/oss-fuzz/dummy-cmd-main.c
new file mode 100644
index 0000000..071cb23
--- /dev/null
+++ b/oss-fuzz/dummy-cmd-main.c
@@ -0,0 +1,14 @@
+#include "git-compat-util.h"
+
+/*
+ * When linking the fuzzers, we link against common-main.o to pick up some
+ * symbols. However, even though we ignore common-main:main(), we still need to
+ * provide all the symbols it references. In the fuzzers' case, we need to
+ * provide a dummy cmd_main() for the linker to be happy. It will never be
+ * executed.
+ */
+
+int cmd_main(int argc, const char **argv) {
+	BUG("We should not execute cmd_main() from a fuzz target");
+	return 1;
+}
diff --git a/oss-fuzz/fuzz-date.c b/oss-fuzz/fuzz-date.c
new file mode 100644
index 0000000..036378b
--- /dev/null
+++ b/oss-fuzz/fuzz-date.c
@@ -0,0 +1,49 @@
+#include "git-compat-util.h"
+#include "date.h"
+
+int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size);
+
+int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size)
+{
+	int local;
+	int num;
+	char *str;
+	int16_t tz;
+	timestamp_t ts;
+	enum date_mode_type dmtype;
+	struct date_mode *dm;
+
+	if (size <= 4)
+		/*
+		 * we use the first byte to fuzz dmtype and the
+		 * second byte to fuzz local, then the next two
+		 * bytes to fuzz tz offset. The remainder
+		 * (at least one byte) is fed as input to
+		 * approxidate_careful().
+		 */
+		return 0;
+
+	local = !!(*data++ & 0x10);
+	num = *data++ % DATE_UNIX;
+	if (num >= DATE_STRFTIME)
+		num++;
+	dmtype = (enum date_mode_type)num;
+	size -= 2;
+
+	tz = *data++;
+	tz = (tz << 8) | *data++;
+	size -= 2;
+
+	str = xmemdupz(data, size);
+
+	ts = approxidate_careful(str, &num);
+	free(str);
+
+	dm = date_mode_from_type(dmtype);
+	dm->local = local;
+	show_date(ts, (int)tz, dm);
+
+	date_mode_release(dm);
+
+	return 0;
+}
diff --git a/pack-bitmap-write.c b/pack-bitmap-write.c
index be4733e..990a949 100644
--- a/pack-bitmap-write.c
+++ b/pack-bitmap-write.c
@@ -195,6 +195,13 @@ struct bb_commit {
 	unsigned idx; /* within selected array */
 };
 
+static void clear_bb_commit(struct bb_commit *commit)
+{
+	free_commit_list(commit->reverse_edges);
+	bitmap_free(commit->commit_mask);
+	bitmap_free(commit->bitmap);
+}
+
 define_commit_slab(bb_data, struct bb_commit);
 
 struct bitmap_builder {
@@ -336,7 +343,7 @@ static void bitmap_builder_init(struct bitmap_builder *bb,
 
 static void bitmap_builder_clear(struct bitmap_builder *bb)
 {
-	clear_bb_data(&bb->data);
+	deep_clear_bb_data(&bb->data, clear_bb_commit);
 	free(bb->commits);
 	bb->commits_nr = bb->commits_alloc = 0;
 }
diff --git a/pack-bitmap.c b/pack-bitmap.c
index c88dd35..2baeaba 100644
--- a/pack-bitmap.c
+++ b/pack-bitmap.c
@@ -331,7 +331,7 @@ static int open_midx_bitmap_1(struct bitmap_index *bitmap_git,
 	struct stat st;
 	char *bitmap_name = midx_bitmap_filename(midx);
 	int fd = git_open(bitmap_name);
-	uint32_t i;
+	uint32_t i, preferred_pack;
 	struct packed_git *preferred;
 
 	if (fd < 0) {
@@ -386,7 +386,12 @@ static int open_midx_bitmap_1(struct bitmap_index *bitmap_git,
 		}
 	}
 
-	preferred = bitmap_git->midx->packs[midx_preferred_pack(bitmap_git)];
+	if (midx_preferred_pack(bitmap_git->midx, &preferred_pack) < 0) {
+		warning(_("could not determine MIDX preferred pack"));
+		goto cleanup;
+	}
+
+	preferred = bitmap_git->midx->packs[preferred_pack];
 	if (!is_pack_valid(preferred)) {
 		warning(_("preferred pack (%s) is invalid"),
 			preferred->pack_name);
@@ -1273,6 +1278,8 @@ static struct bitmap *find_objects(struct bitmap_index *bitmap_git,
 		base = fill_in_bitmap(bitmap_git, revs, base, seen);
 	}
 
+	object_list_free(&not_mapped);
+
 	return base;
 }
 
@@ -1827,8 +1834,10 @@ struct bitmap_index *prepare_bitmap_walk(struct rev_info *revs,
  * -1 means "stop trying further objects"; 0 means we may or may not have
  * reused, but you can keep feeding bits.
  */
-static int try_partial_reuse(struct packed_git *pack,
-			     size_t pos,
+static int try_partial_reuse(struct bitmap_index *bitmap_git,
+			     struct bitmapped_pack *pack,
+			     size_t bitmap_pos,
+			     uint32_t pack_pos,
 			     struct bitmap *reuse,
 			     struct pack_window **w_curs)
 {
@@ -1836,40 +1845,18 @@ static int try_partial_reuse(struct packed_git *pack,
 	enum object_type type;
 	unsigned long size;
 
-	/*
-	 * try_partial_reuse() is called either on (a) objects in the
-	 * bitmapped pack (in the case of a single-pack bitmap) or (b)
-	 * objects in the preferred pack of a multi-pack bitmap.
-	 * Importantly, the latter can pretend as if only a single pack
-	 * exists because:
-	 *
-	 *   - The first pack->num_objects bits of a MIDX bitmap are
-	 *     reserved for the preferred pack, and
-	 *
-	 *   - Ties due to duplicate objects are always resolved in
-	 *     favor of the preferred pack.
-	 *
-	 * Therefore we do not need to ever ask the MIDX for its copy of
-	 * an object by OID, since it will always select it from the
-	 * preferred pack. Likewise, the selected copy of the base
-	 * object for any deltas will reside in the same pack.
-	 *
-	 * This means that we can reuse pos when looking up the bit in
-	 * the reuse bitmap, too, since bits corresponding to the
-	 * preferred pack precede all bits from other packs.
-	 */
+	if (pack_pos >= pack->p->num_objects)
+		return -1; /* not actually in the pack */
 
-	if (pos >= pack->num_objects)
-		return -1; /* not actually in the pack or MIDX preferred pack */
-
-	offset = delta_obj_offset = pack_pos_to_offset(pack, pos);
-	type = unpack_object_header(pack, w_curs, &offset, &size);
+	offset = delta_obj_offset = pack_pos_to_offset(pack->p, pack_pos);
+	type = unpack_object_header(pack->p, w_curs, &offset, &size);
 	if (type < 0)
 		return -1; /* broken packfile, punt */
 
 	if (type == OBJ_REF_DELTA || type == OBJ_OFS_DELTA) {
 		off_t base_offset;
 		uint32_t base_pos;
+		uint32_t base_bitmap_pos;
 
 		/*
 		 * Find the position of the base object so we can look it up
@@ -1879,24 +1866,48 @@ static int try_partial_reuse(struct packed_git *pack,
 		 * and the normal slow path will complain about it in
 		 * more detail.
 		 */
-		base_offset = get_delta_base(pack, w_curs, &offset, type,
+		base_offset = get_delta_base(pack->p, w_curs, &offset, type,
 					     delta_obj_offset);
 		if (!base_offset)
 			return 0;
-		if (offset_to_pack_pos(pack, base_offset, &base_pos) < 0)
-			return 0;
 
-		/*
-		 * We assume delta dependencies always point backwards. This
-		 * lets us do a single pass, and is basically always true
-		 * due to the way OFS_DELTAs work. You would not typically
-		 * find REF_DELTA in a bitmapped pack, since we only bitmap
-		 * packs we write fresh, and OFS_DELTA is the default). But
-		 * let's double check to make sure the pack wasn't written with
-		 * odd parameters.
-		 */
-		if (base_pos >= pos)
-			return 0;
+		offset_to_pack_pos(pack->p, base_offset, &base_pos);
+
+		if (bitmap_is_midx(bitmap_git)) {
+			/*
+			 * Cross-pack deltas are rejected for now, but could
+			 * theoretically be supported in the future.
+			 *
+			 * We would need to ensure that we're sending both
+			 * halves of the delta/base pair, regardless of whether
+			 * or not the two cross a pack boundary. If they do,
+			 * then we must convert the delta to an REF_DELTA to
+			 * refer back to the base in the other pack.
+			 * */
+			if (midx_pair_to_pack_pos(bitmap_git->midx,
+						  pack->pack_int_id,
+						  base_offset,
+						  &base_bitmap_pos) < 0) {
+				return 0;
+			}
+		} else {
+			if (offset_to_pack_pos(pack->p, base_offset,
+					       &base_pos) < 0)
+				return 0;
+			/*
+			 * We assume delta dependencies always point backwards.
+			 * This lets us do a single pass, and is basically
+			 * always true due to the way OFS_DELTAs work. You would
+			 * not typically find REF_DELTA in a bitmapped pack,
+			 * since we only bitmap packs we write fresh, and
+			 * OFS_DELTA is the default). But let's double check to
+			 * make sure the pack wasn't written with odd
+			 * parameters.
+			 */
+			if (base_pos >= pack_pos)
+				return 0;
+			base_bitmap_pos = pack->bitmap_pos + base_pos;
+		}
 
 		/*
 		 * And finally, if we're not sending the base as part of our
@@ -1906,77 +1917,89 @@ static int try_partial_reuse(struct packed_git *pack,
 		 * to REF_DELTA on the fly. Better to just let the normal
 		 * object_entry code path handle it.
 		 */
-		if (!bitmap_get(reuse, base_pos))
+		if (!bitmap_get(reuse, base_bitmap_pos))
 			return 0;
 	}
 
 	/*
 	 * If we got here, then the object is OK to reuse. Mark it.
 	 */
-	bitmap_set(reuse, pos);
+	bitmap_set(reuse, bitmap_pos);
 	return 0;
 }
 
-uint32_t midx_preferred_pack(struct bitmap_index *bitmap_git)
+static void reuse_partial_packfile_from_bitmap_1(struct bitmap_index *bitmap_git,
+						 struct bitmapped_pack *pack,
+						 struct bitmap *reuse)
 {
-	struct multi_pack_index *m = bitmap_git->midx;
-	if (!m)
-		BUG("midx_preferred_pack: requires non-empty MIDX");
-	return nth_midxed_pack_int_id(m, pack_pos_to_midx(bitmap_git->midx, 0));
-}
-
-int reuse_partial_packfile_from_bitmap(struct bitmap_index *bitmap_git,
-				       struct packed_git **packfile_out,
-				       uint32_t *entries,
-				       struct bitmap **reuse_out)
-{
-	struct repository *r = the_repository;
-	struct packed_git *pack;
 	struct bitmap *result = bitmap_git->result;
-	struct bitmap *reuse;
 	struct pack_window *w_curs = NULL;
-	size_t i = 0;
-	uint32_t offset;
-	uint32_t objects_nr;
+	size_t pos = pack->bitmap_pos / BITS_IN_EWORD;
 
-	assert(result);
+	if (!pack->bitmap_pos) {
+		/*
+		 * If we're processing the first (in the case of a MIDX, the
+		 * preferred pack) or the only (in the case of single-pack
+		 * bitmaps) pack, then we can reuse whole words at a time.
+		 *
+		 * This is because we know that any deltas in this range *must*
+		 * have their bases chosen from the same pack, since:
+		 *
+		 * - In the single pack case, there is no other pack to choose
+		 *   them from.
+		 *
+		 * - In the MIDX case, the first pack is the preferred pack, so
+		 *   all ties are broken in favor of that pack (i.e. the one
+		 *   we're currently processing). So any duplicate bases will be
+		 *   resolved in favor of the pack we're processing.
+		 */
+		while (pos < result->word_alloc &&
+		       pos < pack->bitmap_nr / BITS_IN_EWORD &&
+		       result->words[pos] == (eword_t)~0)
+			pos++;
+		memset(reuse->words, 0xFF, pos * sizeof(eword_t));
+	}
 
-	load_reverse_index(r, bitmap_git);
+	for (; pos < result->word_alloc; pos++) {
+		eword_t word = result->words[pos];
+		size_t offset;
 
-	if (bitmap_is_midx(bitmap_git))
-		pack = bitmap_git->midx->packs[midx_preferred_pack(bitmap_git)];
-	else
-		pack = bitmap_git->pack;
-	objects_nr = pack->num_objects;
+		for (offset = 0; offset < BITS_IN_EWORD; offset++) {
+			size_t bit_pos;
+			uint32_t pack_pos;
 
-	while (i < result->word_alloc && result->words[i] == (eword_t)~0)
-		i++;
-
-	/*
-	 * Don't mark objects not in the packfile or preferred pack. This bitmap
-	 * marks objects eligible for reuse, but the pack-reuse code only
-	 * understands how to reuse a single pack. Since the preferred pack is
-	 * guaranteed to have all bases for its deltas (in a multi-pack bitmap),
-	 * we use it instead of another pack. In single-pack bitmaps, the choice
-	 * is made for us.
-	 */
-	if (i > objects_nr / BITS_IN_EWORD)
-		i = objects_nr / BITS_IN_EWORD;
-
-	reuse = bitmap_word_alloc(i);
-	memset(reuse->words, 0xFF, i * sizeof(eword_t));
-
-	for (; i < result->word_alloc; ++i) {
-		eword_t word = result->words[i];
-		size_t pos = (i * BITS_IN_EWORD);
-
-		for (offset = 0; offset < BITS_IN_EWORD; ++offset) {
-			if ((word >> offset) == 0)
+			if (word >> offset == 0)
 				break;
 
 			offset += ewah_bit_ctz64(word >> offset);
-			if (try_partial_reuse(pack, pos + offset,
-					      reuse, &w_curs) < 0) {
+
+			bit_pos = pos * BITS_IN_EWORD + offset;
+			if (bit_pos < pack->bitmap_pos)
+				continue;
+			if (bit_pos >= pack->bitmap_pos + pack->bitmap_nr)
+				goto done;
+
+			if (bitmap_is_midx(bitmap_git)) {
+				uint32_t midx_pos;
+				off_t ofs;
+
+				midx_pos = pack_pos_to_midx(bitmap_git->midx, bit_pos);
+				ofs = nth_midxed_offset(bitmap_git->midx, midx_pos);
+
+				if (offset_to_pack_pos(pack->p, ofs, &pack_pos) < 0)
+					BUG("could not find object in pack %s "
+					    "at offset %"PRIuMAX" in MIDX",
+					    pack_basename(pack->p), (uintmax_t)ofs);
+			} else {
+				pack_pos = cast_size_t_to_uint32_t(st_sub(bit_pos, pack->bitmap_pos));
+				if (pack_pos >= pack->p->num_objects)
+					BUG("advanced beyond the end of pack %s (%"PRIuMAX" > %"PRIu32")",
+					    pack_basename(pack->p), (uintmax_t)pack_pos,
+					    pack->p->num_objects);
+			}
+
+			if (try_partial_reuse(bitmap_git, pack, bit_pos,
+					      pack_pos, reuse, &w_curs) < 0) {
 				/*
 				 * try_partial_reuse indicated we couldn't reuse
 				 * any bits, so there is no point in trying more
@@ -1993,11 +2016,97 @@ int reuse_partial_packfile_from_bitmap(struct bitmap_index *bitmap_git,
 
 done:
 	unuse_pack(&w_curs);
+}
 
-	*entries = bitmap_popcount(reuse);
-	if (!*entries) {
-		bitmap_free(reuse);
+static int bitmapped_pack_cmp(const void *va, const void *vb)
+{
+	const struct bitmapped_pack *a = va;
+	const struct bitmapped_pack *b = vb;
+
+	if (a->bitmap_pos < b->bitmap_pos)
 		return -1;
+	if (a->bitmap_pos > b->bitmap_pos)
+		return 1;
+	return 0;
+}
+
+void reuse_partial_packfile_from_bitmap(struct bitmap_index *bitmap_git,
+					struct bitmapped_pack **packs_out,
+					size_t *packs_nr_out,
+					struct bitmap **reuse_out,
+					int multi_pack_reuse)
+{
+	struct repository *r = the_repository;
+	struct bitmapped_pack *packs = NULL;
+	struct bitmap *result = bitmap_git->result;
+	struct bitmap *reuse;
+	size_t i;
+	size_t packs_nr = 0, packs_alloc = 0;
+	size_t word_alloc;
+	uint32_t objects_nr = 0;
+
+	assert(result);
+
+	load_reverse_index(r, bitmap_git);
+
+	if (bitmap_is_midx(bitmap_git)) {
+		for (i = 0; i < bitmap_git->midx->num_packs; i++) {
+			struct bitmapped_pack pack;
+			if (nth_bitmapped_pack(r, bitmap_git->midx, &pack, i) < 0) {
+				warning(_("unable to load pack: '%s', disabling pack-reuse"),
+					bitmap_git->midx->pack_names[i]);
+				free(packs);
+				return;
+			}
+
+			if (!pack.bitmap_nr)
+				continue;
+
+			if (!multi_pack_reuse && pack.bitmap_pos) {
+				/*
+				 * If we're only reusing a single pack, skip
+				 * over any packs which are not positioned at
+				 * the beginning of the MIDX bitmap.
+				 *
+				 * This is consistent with the existing
+				 * single-pack reuse behavior, which only reuses
+				 * parts of the MIDX's preferred pack.
+				 */
+				continue;
+			}
+
+			ALLOC_GROW(packs, packs_nr + 1, packs_alloc);
+			memcpy(&packs[packs_nr++], &pack, sizeof(pack));
+
+			objects_nr += pack.p->num_objects;
+
+			if (!multi_pack_reuse)
+				break;
+		}
+
+		QSORT(packs, packs_nr, bitmapped_pack_cmp);
+	} else {
+		ALLOC_GROW(packs, packs_nr + 1, packs_alloc);
+
+		packs[packs_nr].p = bitmap_git->pack;
+		packs[packs_nr].bitmap_nr = bitmap_git->pack->num_objects;
+		packs[packs_nr].bitmap_pos = 0;
+
+		objects_nr = packs[packs_nr++].bitmap_nr;
+	}
+
+	word_alloc = objects_nr / BITS_IN_EWORD;
+	if (objects_nr % BITS_IN_EWORD)
+		word_alloc++;
+	reuse = bitmap_word_alloc(word_alloc);
+
+	for (i = 0; i < packs_nr; i++)
+		reuse_partial_packfile_from_bitmap_1(bitmap_git, &packs[i], reuse);
+
+	if (bitmap_is_empty(reuse)) {
+		free(packs);
+		bitmap_free(reuse);
+		return;
 	}
 
 	/*
@@ -2005,9 +2114,9 @@ int reuse_partial_packfile_from_bitmap(struct bitmap_index *bitmap_git,
 	 * need to be handled separately.
 	 */
 	bitmap_and_not(result, reuse);
-	*packfile_out = pack;
+	*packs_out = packs;
+	*packs_nr_out = packs_nr;
 	*reuse_out = reuse;
-	return 0;
 }
 
 int bitmap_walk_contains(struct bitmap_index *bitmap_git,
diff --git a/pack-bitmap.h b/pack-bitmap.h
index 5273a6a..c7dea13 100644
--- a/pack-bitmap.h
+++ b/pack-bitmap.h
@@ -52,6 +52,15 @@ typedef int (*show_reachable_fn)(
 
 struct bitmap_index;
 
+struct bitmapped_pack {
+	struct packed_git *p;
+
+	uint32_t bitmap_pos;
+	uint32_t bitmap_nr;
+
+	uint32_t pack_int_id; /* MIDX only */
+};
+
 struct bitmap_index *prepare_bitmap_git(struct repository *r);
 struct bitmap_index *prepare_midx_bitmap_git(struct multi_pack_index *midx);
 void count_bitmap_commit_list(struct bitmap_index *, uint32_t *commits,
@@ -68,11 +77,11 @@ int test_bitmap_hashes(struct repository *r);
 
 struct bitmap_index *prepare_bitmap_walk(struct rev_info *revs,
 					 int filter_provided_objects);
-uint32_t midx_preferred_pack(struct bitmap_index *bitmap_git);
-int reuse_partial_packfile_from_bitmap(struct bitmap_index *,
-				       struct packed_git **packfile,
-				       uint32_t *entries,
-				       struct bitmap **reuse_out);
+void reuse_partial_packfile_from_bitmap(struct bitmap_index *bitmap_git,
+					struct bitmapped_pack **packs_out,
+					size_t *packs_nr_out,
+					struct bitmap **reuse_out,
+					int multi_pack_reuse);
 int rebuild_existing_bitmaps(struct bitmap_index *, struct packing_data *mapping,
 			     kh_oid_map_t *reused_bitmaps, int show_progress);
 void free_bitmap_index(struct bitmap_index *);
diff --git a/pack-objects.c b/pack-objects.c
index f403ca6..a9d9855 100644
--- a/pack-objects.c
+++ b/pack-objects.c
@@ -151,6 +151,21 @@ void prepare_packing_data(struct repository *r, struct packing_data *pdata)
 	init_recursive_mutex(&pdata->odb_lock);
 }
 
+void clear_packing_data(struct packing_data *pdata)
+{
+	if (!pdata)
+		return;
+
+	free(pdata->cruft_mtime);
+	free(pdata->in_pack);
+	free(pdata->in_pack_by_idx);
+	free(pdata->in_pack_pos);
+	free(pdata->index);
+	free(pdata->layer);
+	free(pdata->objects);
+	free(pdata->tree_depth);
+}
+
 struct object_entry *packlist_alloc(struct packing_data *pdata,
 				    const struct object_id *oid)
 {
diff --git a/pack-objects.h b/pack-objects.h
index 0d78db4..b9898a4 100644
--- a/pack-objects.h
+++ b/pack-objects.h
@@ -169,6 +169,7 @@ struct packing_data {
 };
 
 void prepare_packing_data(struct repository *r, struct packing_data *pdata);
+void clear_packing_data(struct packing_data *pdata);
 
 /* Protect access to object database */
 static inline void packing_data_lock(struct packing_data *pdata)
diff --git a/pack-revindex.c b/pack-revindex.c
index acf1dd9..a7624d8 100644
--- a/pack-revindex.c
+++ b/pack-revindex.c
@@ -520,19 +520,12 @@ static int midx_pack_order_cmp(const void *va, const void *vb)
 	return 0;
 }
 
-int midx_to_pack_pos(struct multi_pack_index *m, uint32_t at, uint32_t *pos)
+static int midx_key_to_pack_pos(struct multi_pack_index *m,
+				struct midx_pack_key *key,
+				uint32_t *pos)
 {
-	struct midx_pack_key key;
 	uint32_t *found;
 
-	if (!m->revindex_data)
-		BUG("midx_to_pack_pos: reverse index not yet loaded");
-	if (m->num_objects <= at)
-		BUG("midx_to_pack_pos: out-of-bounds object at %"PRIu32, at);
-
-	key.pack = nth_midxed_pack_int_id(m, at);
-	key.offset = nth_midxed_offset(m, at);
-	key.midx = m;
 	/*
 	 * The preferred pack sorts first, so determine its identifier by
 	 * looking at the first object in pseudo-pack order.
@@ -542,14 +535,43 @@ int midx_to_pack_pos(struct multi_pack_index *m, uint32_t at, uint32_t *pos)
 	 * implicitly is preferred (and includes all its objects, since ties are
 	 * broken first by pack identifier).
 	 */
-	key.preferred_pack = nth_midxed_pack_int_id(m, pack_pos_to_midx(m, 0));
+	if (midx_preferred_pack(key->midx, &key->preferred_pack) < 0)
+		return error(_("could not determine preferred pack"));
 
-	found = bsearch(&key, m->revindex_data, m->num_objects,
-			sizeof(*m->revindex_data), midx_pack_order_cmp);
+	found = bsearch(key, m->revindex_data, m->num_objects,
+			sizeof(*m->revindex_data),
+			midx_pack_order_cmp);
 
 	if (!found)
-		return error("bad offset for revindex");
+		return -1;
 
 	*pos = found - m->revindex_data;
 	return 0;
 }
+
+int midx_to_pack_pos(struct multi_pack_index *m, uint32_t at, uint32_t *pos)
+{
+	struct midx_pack_key key;
+
+	if (!m->revindex_data)
+		BUG("midx_to_pack_pos: reverse index not yet loaded");
+	if (m->num_objects <= at)
+		BUG("midx_to_pack_pos: out-of-bounds object at %"PRIu32, at);
+
+	key.pack = nth_midxed_pack_int_id(m, at);
+	key.offset = nth_midxed_offset(m, at);
+	key.midx = m;
+
+	return midx_key_to_pack_pos(m, &key, pos);
+}
+
+int midx_pair_to_pack_pos(struct multi_pack_index *m, uint32_t pack_int_id,
+			  off_t ofs, uint32_t *pos)
+{
+	struct midx_pack_key key = {
+		.pack = pack_int_id,
+		.offset = ofs,
+		.midx = m,
+	};
+	return midx_key_to_pack_pos(m, &key, pos);
+}
diff --git a/pack-revindex.h b/pack-revindex.h
index 6dd47ef..422c248 100644
--- a/pack-revindex.h
+++ b/pack-revindex.h
@@ -142,4 +142,7 @@ uint32_t pack_pos_to_midx(struct multi_pack_index *m, uint32_t pos);
  */
 int midx_to_pack_pos(struct multi_pack_index *midx, uint32_t at, uint32_t *pos);
 
+int midx_pair_to_pack_pos(struct multi_pack_index *midx, uint32_t pack_id,
+			  off_t ofs, uint32_t *pos);
+
 #endif
diff --git a/path.c b/path.c
index 67e2690..0fb5279 100644
--- a/path.c
+++ b/path.c
@@ -1588,7 +1588,5 @@ REPO_GIT_PATH_FUNC(merge_msg, "MERGE_MSG")
 REPO_GIT_PATH_FUNC(merge_rr, "MERGE_RR")
 REPO_GIT_PATH_FUNC(merge_mode, "MERGE_MODE")
 REPO_GIT_PATH_FUNC(merge_head, "MERGE_HEAD")
-REPO_GIT_PATH_FUNC(merge_autostash, "MERGE_AUTOSTASH")
-REPO_GIT_PATH_FUNC(auto_merge, "AUTO_MERGE")
 REPO_GIT_PATH_FUNC(fetch_head, "FETCH_HEAD")
 REPO_GIT_PATH_FUNC(shallow, "shallow")
diff --git a/path.h b/path.h
index 639372e..b3233c5 100644
--- a/path.h
+++ b/path.h
@@ -175,8 +175,6 @@ const char *git_path_merge_msg(struct repository *r);
 const char *git_path_merge_rr(struct repository *r);
 const char *git_path_merge_mode(struct repository *r);
 const char *git_path_merge_head(struct repository *r);
-const char *git_path_merge_autostash(struct repository *r);
-const char *git_path_auto_merge(struct repository *r);
 const char *git_path_fetch_head(struct repository *r);
 const char *git_path_shallow(struct repository *r);
 
diff --git a/pathspec.c b/pathspec.c
index bb1efe1..2133b9f 100644
--- a/pathspec.c
+++ b/pathspec.c
@@ -109,16 +109,37 @@ static struct pathspec_magic {
 	{ PATHSPEC_ATTR,    '\0', "attr" },
 };
 
-static void prefix_magic(struct strbuf *sb, int prefixlen, unsigned magic)
+static void prefix_magic(struct strbuf *sb, int prefixlen,
+			 unsigned magic, const char *element)
 {
-	int i;
-	strbuf_addstr(sb, ":(");
-	for (i = 0; i < ARRAY_SIZE(pathspec_magic); i++)
-		if (magic & pathspec_magic[i].bit) {
-			if (sb->buf[sb->len - 1] != '(')
-				strbuf_addch(sb, ',');
-			strbuf_addstr(sb, pathspec_magic[i].name);
+	/* No magic was found in element, just add prefix magic */
+	if (!magic) {
+		strbuf_addf(sb, ":(prefix:%d)", prefixlen);
+		return;
+	}
+
+	/*
+	 * At this point, we know that parse_element_magic() was able
+	 * to extract some pathspec magic from element. So we know
+	 * element is correctly formatted in either shorthand or
+	 * longhand form
+	 */
+	if (element[1] != '(') {
+		/* Process an element in shorthand form (e.g. ":!/<match>") */
+		strbuf_addstr(sb, ":(");
+		for (int i = 0; i < ARRAY_SIZE(pathspec_magic); i++) {
+			if ((magic & pathspec_magic[i].bit) &&
+			    pathspec_magic[i].mnemonic) {
+				if (sb->buf[sb->len - 1] != '(')
+					strbuf_addch(sb, ',');
+				strbuf_addstr(sb, pathspec_magic[i].name);
+			}
 		}
+	} else {
+		/* For the longhand form, we copy everything up to the final ')' */
+		size_t len = strchr(element, ')') - element;
+		strbuf_add(sb, element, len);
+	}
 	strbuf_addf(sb, ",prefix:%d)", prefixlen);
 }
 
@@ -493,7 +514,7 @@ static void init_pathspec_item(struct pathspec_item *item, unsigned flags,
 		struct strbuf sb = STRBUF_INIT;
 
 		/* Preserve the actual prefix length of each pattern */
-		prefix_magic(&sb, prefixlen, element_magic);
+		prefix_magic(&sb, prefixlen, element_magic, elt);
 
 		strbuf_addstr(&sb, match);
 		item->original = strbuf_detach(&sb, NULL);
diff --git a/read-cache-ll.h b/read-cache-ll.h
index 9a1a7ed..2a50a78 100644
--- a/read-cache-ll.h
+++ b/read-cache-ll.h
@@ -436,6 +436,14 @@ int match_stat_data_racy(const struct index_state *istate,
 
 void fill_stat_cache_info(struct index_state *istate, struct cache_entry *ce, struct stat *st);
 
+/*
+ * Fill members of st by members of sd enough to convince match_stat()
+ * to consider that they match.  It should be usable as a replacement
+ * for lstat() for a tracked path that is known to be up-to-date via
+ * some out-of-line means (like fsmonitor).
+ */
+int fake_lstat(const struct cache_entry *ce, struct stat *st);
+
 #define REFRESH_REALLY                   (1 << 0) /* ignore_valid */
 #define REFRESH_UNMERGED                 (1 << 1) /* allow unmerged */
 #define REFRESH_QUIET                    (1 << 2) /* be quiet about it */
diff --git a/read-cache.c b/read-cache.c
index 08970ca..f546cf7 100644
--- a/read-cache.c
+++ b/read-cache.c
@@ -195,6 +195,33 @@ void fill_stat_cache_info(struct index_state *istate, struct cache_entry *ce, st
 	}
 }
 
+static unsigned int st_mode_from_ce(const struct cache_entry *ce)
+{
+	extern int trust_executable_bit, has_symlinks;
+
+	switch (ce->ce_mode & S_IFMT) {
+	case S_IFLNK:
+		return has_symlinks ? S_IFLNK : (S_IFREG | 0644);
+	case S_IFREG:
+		return (ce->ce_mode & (trust_executable_bit ? 0755 : 0644)) | S_IFREG;
+	case S_IFGITLINK:
+		return S_IFDIR | 0755;
+	case S_IFDIR:
+		return ce->ce_mode;
+	default:
+		BUG("unsupported ce_mode: %o", ce->ce_mode);
+	}
+}
+
+int fake_lstat(const struct cache_entry *ce, struct stat *st)
+{
+	fake_lstat_data(&ce->ce_stat_data, st);
+	st->st_mode = st_mode_from_ce(ce);
+
+	/* always succeed as lstat() replacement */
+	return 0;
+}
+
 static int ce_compare_data(struct index_state *istate,
 			   const struct cache_entry *ce,
 			   struct stat *st)
diff --git a/ref-filter.c b/ref-filter.c
index 0ac3fca..be14b56 100644
--- a/ref-filter.c
+++ b/ref-filter.c
@@ -1611,6 +1611,12 @@ static void grab_date(const char *buf, struct atom_value *v, const char *atomnam
 	if (formatp) {
 		formatp++;
 		parse_date_format(formatp, &date_mode);
+
+		/*
+		 * If this is a sort field and a format was specified, we'll
+		 * want to compare formatted date by string value.
+		 */
+		v->atom->type = FIELD_STR;
 	}
 
 	if (!eoemail)
@@ -2505,17 +2511,12 @@ static int populate_value(struct ref_array_item *ref, struct strbuf *err)
 		return 0;
 
 	/*
-	 * If it is a tag object, see if we use a value that derefs
-	 * the object, and if we do grab the object it refers to.
+	 * If it is a tag object, see if we use the peeled value. If we do,
+	 * grab the peeled OID.
 	 */
-	oi_deref.oid = *get_tagged_oid((struct tag *)obj);
+	if (need_tagged && peel_iterated_oid(&obj->oid, &oi_deref.oid))
+		die("bad tag");
 
-	/*
-	 * NEEDSWORK: This derefs tag only once, which
-	 * is good to deal with chains of trust, but
-	 * is not consistent with what deref_tag() does
-	 * which peels the onion to the core.
-	 */
 	return get_object(ref, 1, &obj, &oi_deref, err);
 }
 
@@ -2713,15 +2714,18 @@ static struct ref_array_item *new_ref_array_item(const char *refname,
 	return ref;
 }
 
+static void ref_array_append(struct ref_array *array, struct ref_array_item *ref)
+{
+	ALLOC_GROW(array->items, array->nr + 1, array->alloc);
+	array->items[array->nr++] = ref;
+}
+
 struct ref_array_item *ref_array_push(struct ref_array *array,
 				      const char *refname,
 				      const struct object_id *oid)
 {
 	struct ref_array_item *ref = new_ref_array_item(refname, oid);
-
-	ALLOC_GROW(array->items, array->nr + 1, array->alloc);
-	array->items[array->nr++] = ref;
-
+	ref_array_append(array, ref);
 	return ref;
 }
 
@@ -2758,48 +2762,36 @@ static int filter_ref_kind(struct ref_filter *filter, const char *refname)
 	return ref_kind_from_refname(refname);
 }
 
-struct ref_filter_cbdata {
-	struct ref_array *array;
-	struct ref_filter *filter;
-	struct contains_cache contains_cache;
-	struct contains_cache no_contains_cache;
-};
-
-/*
- * A call-back given to for_each_ref().  Filter refs and keep them for
- * later object processing.
- */
-static int ref_filter_handler(const char *refname, const struct object_id *oid, int flag, void *cb_data)
+static struct ref_array_item *apply_ref_filter(const char *refname, const struct object_id *oid,
+			    int flag, struct ref_filter *filter)
 {
-	struct ref_filter_cbdata *ref_cbdata = cb_data;
-	struct ref_filter *filter = ref_cbdata->filter;
 	struct ref_array_item *ref;
 	struct commit *commit = NULL;
 	unsigned int kind;
 
 	if (flag & REF_BAD_NAME) {
 		warning(_("ignoring ref with broken name %s"), refname);
-		return 0;
+		return NULL;
 	}
 
 	if (flag & REF_ISBROKEN) {
 		warning(_("ignoring broken ref %s"), refname);
-		return 0;
+		return NULL;
 	}
 
 	/* Obtain the current ref kind from filter_ref_kind() and ignore unwanted refs. */
 	kind = filter_ref_kind(filter, refname);
 	if (!(kind & filter->kind))
-		return 0;
+		return NULL;
 
 	if (!filter_pattern_match(filter, refname))
-		return 0;
+		return NULL;
 
 	if (filter_exclude_match(filter, refname))
-		return 0;
+		return NULL;
 
 	if (filter->points_at.nr && !match_points_at(&filter->points_at, oid, refname))
-		return 0;
+		return NULL;
 
 	/*
 	 * A merge filter is applied on refs pointing to commits. Hence
@@ -2810,15 +2802,15 @@ static int ref_filter_handler(const char *refname, const struct object_id *oid,
 	    filter->with_commit || filter->no_commit || filter->verbose) {
 		commit = lookup_commit_reference_gently(the_repository, oid, 1);
 		if (!commit)
-			return 0;
+			return NULL;
 		/* We perform the filtering for the '--contains' option... */
 		if (filter->with_commit &&
-		    !commit_contains(filter, commit, filter->with_commit, &ref_cbdata->contains_cache))
-			return 0;
+		    !commit_contains(filter, commit, filter->with_commit, &filter->internal.contains_cache))
+			return NULL;
 		/* ...or for the `--no-contains' option */
 		if (filter->no_commit &&
-		    commit_contains(filter, commit, filter->no_commit, &ref_cbdata->no_contains_cache))
-			return 0;
+		    commit_contains(filter, commit, filter->no_commit, &filter->internal.no_contains_cache))
+			return NULL;
 	}
 
 	/*
@@ -2826,11 +2818,32 @@ static int ref_filter_handler(const char *refname, const struct object_id *oid,
 	 * to do its job and the resulting list may yet to be pruned
 	 * by maxcount logic.
 	 */
-	ref = ref_array_push(ref_cbdata->array, refname, oid);
+	ref = new_ref_array_item(refname, oid);
 	ref->commit = commit;
 	ref->flag = flag;
 	ref->kind = kind;
 
+	return ref;
+}
+
+struct ref_filter_cbdata {
+	struct ref_array *array;
+	struct ref_filter *filter;
+};
+
+/*
+ * A call-back given to for_each_ref().  Filter refs and keep them for
+ * later object processing.
+ */
+static int filter_one(const char *refname, const struct object_id *oid, int flag, void *cb_data)
+{
+	struct ref_filter_cbdata *ref_cbdata = cb_data;
+	struct ref_array_item *ref;
+
+	ref = apply_ref_filter(refname, oid, flag, ref_cbdata->filter);
+	if (ref)
+		ref_array_append(ref_cbdata->array, ref);
+
 	return 0;
 }
 
@@ -2848,6 +2861,49 @@ static void free_array_item(struct ref_array_item *item)
 	free(item);
 }
 
+struct ref_filter_and_format_cbdata {
+	struct ref_filter *filter;
+	struct ref_format *format;
+
+	struct ref_filter_and_format_internal {
+		int count;
+	} internal;
+};
+
+static int filter_and_format_one(const char *refname, const struct object_id *oid, int flag, void *cb_data)
+{
+	struct ref_filter_and_format_cbdata *ref_cbdata = cb_data;
+	struct ref_array_item *ref;
+	struct strbuf output = STRBUF_INIT, err = STRBUF_INIT;
+
+	ref = apply_ref_filter(refname, oid, flag, ref_cbdata->filter);
+	if (!ref)
+		return 0;
+
+	if (format_ref_array_item(ref, ref_cbdata->format, &output, &err))
+		die("%s", err.buf);
+
+	if (output.len || !ref_cbdata->format->array_opts.omit_empty) {
+		fwrite(output.buf, 1, output.len, stdout);
+		putchar('\n');
+	}
+
+	strbuf_release(&output);
+	strbuf_release(&err);
+	free_array_item(ref);
+
+	/*
+	 * Increment the running count of refs that match the filter. If
+	 * max_count is set and we've reached the max, stop the ref
+	 * iteration by returning a nonzero value.
+	 */
+	if (ref_cbdata->format->array_opts.max_count &&
+	    ++ref_cbdata->internal.count >= ref_cbdata->format->array_opts.max_count)
+		return 1;
+
+	return 0;
+}
+
 /* Free all memory allocated for ref_array */
 void ref_array_clear(struct ref_array *array)
 {
@@ -2966,6 +3022,43 @@ void filter_ahead_behind(struct repository *r,
 	free(commits);
 }
 
+static int do_filter_refs(struct ref_filter *filter, unsigned int type, each_ref_fn fn, void *cb_data)
+{
+	int ret = 0;
+
+	filter->kind = type & FILTER_REFS_KIND_MASK;
+
+	init_contains_cache(&filter->internal.contains_cache);
+	init_contains_cache(&filter->internal.no_contains_cache);
+
+	/*  Simple per-ref filtering */
+	if (!filter->kind)
+		die("filter_refs: invalid type");
+	else {
+		/*
+		 * For common cases where we need only branches or remotes or tags,
+		 * we only iterate through those refs. If a mix of refs is needed,
+		 * we iterate over all refs and filter out required refs with the help
+		 * of filter_ref_kind().
+		 */
+		if (filter->kind == FILTER_REFS_BRANCHES)
+			ret = for_each_fullref_in("refs/heads/", fn, cb_data);
+		else if (filter->kind == FILTER_REFS_REMOTES)
+			ret = for_each_fullref_in("refs/remotes/", fn, cb_data);
+		else if (filter->kind == FILTER_REFS_TAGS)
+			ret = for_each_fullref_in("refs/tags/", fn, cb_data);
+		else if (filter->kind & FILTER_REFS_ALL)
+			ret = for_each_fullref_in_pattern(filter, fn, cb_data);
+		if (!ret && (filter->kind & FILTER_REFS_DETACHED_HEAD))
+			head_ref(fn, cb_data);
+	}
+
+	clear_contains_cache(&filter->internal.contains_cache);
+	clear_contains_cache(&filter->internal.no_contains_cache);
+
+	return ret;
+}
+
 /*
  * API for filtering a set of refs. Based on the type of refs the user
  * has requested, we iterate through those refs and apply filters
@@ -2981,38 +3074,10 @@ int filter_refs(struct ref_array *array, struct ref_filter *filter, unsigned int
 	ref_cbdata.array = array;
 	ref_cbdata.filter = filter;
 
-	filter->kind = type & FILTER_REFS_KIND_MASK;
-
 	save_commit_buffer_orig = save_commit_buffer;
 	save_commit_buffer = 0;
 
-	init_contains_cache(&ref_cbdata.contains_cache);
-	init_contains_cache(&ref_cbdata.no_contains_cache);
-
-	/*  Simple per-ref filtering */
-	if (!filter->kind)
-		die("filter_refs: invalid type");
-	else {
-		/*
-		 * For common cases where we need only branches or remotes or tags,
-		 * we only iterate through those refs. If a mix of refs is needed,
-		 * we iterate over all refs and filter out required refs with the help
-		 * of filter_ref_kind().
-		 */
-		if (filter->kind == FILTER_REFS_BRANCHES)
-			ret = for_each_fullref_in("refs/heads/", ref_filter_handler, &ref_cbdata);
-		else if (filter->kind == FILTER_REFS_REMOTES)
-			ret = for_each_fullref_in("refs/remotes/", ref_filter_handler, &ref_cbdata);
-		else if (filter->kind == FILTER_REFS_TAGS)
-			ret = for_each_fullref_in("refs/tags/", ref_filter_handler, &ref_cbdata);
-		else if (filter->kind & FILTER_REFS_ALL)
-			ret = for_each_fullref_in_pattern(filter, ref_filter_handler, &ref_cbdata);
-		if (!ret && (filter->kind & FILTER_REFS_DETACHED_HEAD))
-			head_ref(ref_filter_handler, &ref_cbdata);
-	}
-
-	clear_contains_cache(&ref_cbdata.contains_cache);
-	clear_contains_cache(&ref_cbdata.no_contains_cache);
+	ret = do_filter_refs(filter, type, filter_one, &ref_cbdata);
 
 	/*  Filters that need revision walking */
 	reach_filter(array, &filter->reachable_from, INCLUDE_REACHED);
@@ -3022,6 +3087,51 @@ int filter_refs(struct ref_array *array, struct ref_filter *filter, unsigned int
 	return ret;
 }
 
+static inline int can_do_iterative_format(struct ref_filter *filter,
+					  struct ref_sorting *sorting,
+					  struct ref_format *format)
+{
+	/*
+	 * Filtering & formatting results within a single ref iteration
+	 * callback is not compatible with options that require
+	 * post-processing a filtered ref_array. These include:
+	 * - filtering on reachability
+	 * - sorting the filtered results
+	 * - including ahead-behind information in the formatted output
+	 */
+	return !(filter->reachable_from ||
+		 filter->unreachable_from ||
+		 sorting ||
+		 format->bases.nr);
+}
+
+void filter_and_format_refs(struct ref_filter *filter, unsigned int type,
+			    struct ref_sorting *sorting,
+			    struct ref_format *format)
+{
+	if (can_do_iterative_format(filter, sorting, format)) {
+		int save_commit_buffer_orig;
+		struct ref_filter_and_format_cbdata ref_cbdata = {
+			.filter = filter,
+			.format = format,
+		};
+
+		save_commit_buffer_orig = save_commit_buffer;
+		save_commit_buffer = 0;
+
+		do_filter_refs(filter, type, filter_and_format_one, &ref_cbdata);
+
+		save_commit_buffer = save_commit_buffer_orig;
+	} else {
+		struct ref_array array = { 0 };
+		filter_refs(&array, filter, type);
+		filter_ahead_behind(the_repository, format, &array);
+		ref_array_sort(sorting, &array);
+		print_formatted_ref_array(&array, format);
+		ref_array_clear(&array);
+	}
+}
+
 static int compare_detached_head(struct ref_array_item *a, struct ref_array_item *b)
 {
 	if (!(a->kind ^ b->kind))
@@ -3139,7 +3249,8 @@ void ref_sorting_set_sort_flags_all(struct ref_sorting *sorting,
 
 void ref_array_sort(struct ref_sorting *sorting, struct ref_array *array)
 {
-	QSORT_S(array->items, array->nr, compare_refs, sorting);
+	if (sorting)
+		QSORT_S(array->items, array->nr, compare_refs, sorting);
 }
 
 static void append_literal(const char *cp, const char *ep, struct ref_formatting_state *state)
@@ -3210,6 +3321,29 @@ int format_ref_array_item(struct ref_array_item *info,
 	return 0;
 }
 
+void print_formatted_ref_array(struct ref_array *array, struct ref_format *format)
+{
+	int total;
+	struct strbuf output = STRBUF_INIT, err = STRBUF_INIT;
+
+	total = format->array_opts.max_count;
+	if (!total || array->nr < total)
+		total = array->nr;
+	for (int i = 0; i < total; i++) {
+		strbuf_reset(&err);
+		strbuf_reset(&output);
+		if (format_ref_array_item(array->items[i], format, &output, &err))
+			die("%s", err.buf);
+		if (output.len || !format->array_opts.omit_empty) {
+			fwrite(output.buf, 1, output.len, stdout);
+			putchar('\n');
+		}
+	}
+
+	strbuf_release(&err);
+	strbuf_release(&output);
+}
+
 void pretty_print_ref(const char *name, const struct object_id *oid,
 		      struct ref_format *format)
 {
@@ -3245,18 +3379,6 @@ static int parse_sorting_atom(const char *atom)
 	return res;
 }
 
-/*  If no sorting option is given, use refname to sort as default */
-static struct ref_sorting *ref_default_sorting(void)
-{
-	static const char cstr_name[] = "refname";
-
-	struct ref_sorting *sorting = xcalloc(1, sizeof(*sorting));
-
-	sorting->next = NULL;
-	sorting->atom = parse_sorting_atom(cstr_name);
-	return sorting;
-}
-
 static void parse_ref_sorting(struct ref_sorting **sorting_tail, const char *arg)
 {
 	struct ref_sorting *s;
@@ -3280,9 +3402,7 @@ struct ref_sorting *ref_sorting_options(struct string_list *options)
 	struct string_list_item *item;
 	struct ref_sorting *sorting = NULL, **tail = &sorting;
 
-	if (!options->nr) {
-		sorting = ref_default_sorting();
-	} else {
+	if (options->nr) {
 		for_each_string_list_item(item, options)
 			parse_ref_sorting(tail, item->string);
 	}
diff --git a/ref-filter.h b/ref-filter.h
index 4ecb6ab..07cd6f6 100644
--- a/ref-filter.h
+++ b/ref-filter.h
@@ -6,6 +6,7 @@
 #include "commit.h"
 #include "string-list.h"
 #include "strvec.h"
+#include "commit-reach.h"
 
 /* Quoting styles */
 #define QUOTE_NONE 0
@@ -74,6 +75,11 @@ struct ref_filter {
 		lines;
 	int abbrev,
 		verbose;
+
+	struct {
+		struct contains_cache contains_cache;
+		struct contains_cache no_contains_cache;
+	} internal;
 };
 
 struct ref_format {
@@ -91,6 +97,11 @@ struct ref_format {
 
 	/* List of bases for ahead-behind counts. */
 	struct string_list bases;
+
+	struct {
+		int max_count;
+		int omit_empty;
+	} array_opts;
 };
 
 #define REF_FILTER_INIT { \
@@ -125,6 +136,14 @@ struct ref_format {
  * filtered refs in the ref_array structure.
  */
 int filter_refs(struct ref_array *array, struct ref_filter *filter, unsigned int type);
+/*
+ * Filter refs using the given ref_filter and type, sort the contents
+ * according to the given ref_sorting, format the filtered refs with the
+ * given ref_format, and print them to stdout.
+ */
+void filter_and_format_refs(struct ref_filter *filter, unsigned int type,
+			    struct ref_sorting *sorting,
+			    struct ref_format *format);
 /*  Clear all memory allocated to ref_array */
 void ref_array_clear(struct ref_array *array);
 /*  Used to verify if the given format is correct and to parse out the used atoms */
@@ -150,6 +169,12 @@ char *get_head_description(void);
 void setup_ref_filter_porcelain_msg(void);
 
 /*
+ * Print up to maxcount ref_array elements to stdout using the given
+ * ref_format.
+ */
+void print_formatted_ref_array(struct ref_array *array, struct ref_format *format);
+
+/*
  * Print a single ref, outside of any ref-filter. Note that the
  * name must be a fully qualified refname.
  */
diff --git a/refs.c b/refs.c
index fcae5dd..c633abf 100644
--- a/refs.c
+++ b/refs.c
@@ -33,17 +33,33 @@
 /*
  * List of all available backends
  */
-static struct ref_storage_be *refs_backends = &refs_be_files;
+static const struct ref_storage_be *refs_backends[] = {
+	[REF_STORAGE_FORMAT_FILES] = &refs_be_files,
+};
 
-static struct ref_storage_be *find_ref_storage_backend(const char *name)
+static const struct ref_storage_be *find_ref_storage_backend(unsigned int ref_storage_format)
 {
-	struct ref_storage_be *be;
-	for (be = refs_backends; be; be = be->next)
-		if (!strcmp(be->name, name))
-			return be;
+	if (ref_storage_format < ARRAY_SIZE(refs_backends))
+		return refs_backends[ref_storage_format];
 	return NULL;
 }
 
+unsigned int ref_storage_format_by_name(const char *name)
+{
+	for (unsigned int i = 0; i < ARRAY_SIZE(refs_backends); i++)
+		if (refs_backends[i] && !strcmp(refs_backends[i]->name, name))
+			return i;
+	return REF_STORAGE_FORMAT_UNKNOWN;
+}
+
+const char *ref_storage_format_to_name(unsigned int ref_storage_format)
+{
+	const struct ref_storage_be *be = find_ref_storage_backend(ref_storage_format);
+	if (!be)
+		return "unknown";
+	return be->name;
+}
+
 /*
  * How to handle various characters in refnames:
  * 0: An acceptable character for refs
@@ -1806,8 +1822,10 @@ static int refs_read_special_head(struct ref_store *ref_store,
 	int result = -1;
 	strbuf_addf(&full_path, "%s/%s", ref_store->gitdir, refname);
 
-	if (strbuf_read_file(&content, full_path.buf, 0) < 0)
+	if (strbuf_read_file(&content, full_path.buf, 0) < 0) {
+		*failure_errno = errno;
 		goto done;
+	}
 
 	result = parse_loose_ref_contents(content.buf, oid, referent, type,
 					  failure_errno);
@@ -1818,15 +1836,45 @@ static int refs_read_special_head(struct ref_store *ref_store,
 	return result;
 }
 
+static int is_special_ref(const char *refname)
+{
+	/*
+	 * Special references are refs that have different semantics compared
+	 * to "normal" refs. These refs can thus not be stored in the ref
+	 * backend, but must always be accessed via the filesystem. The
+	 * following refs are special:
+	 *
+	 * - FETCH_HEAD may contain multiple object IDs, and each one of them
+	 *   carries additional metadata like where it came from.
+	 *
+	 * - MERGE_HEAD may contain multiple object IDs when merging multiple
+	 *   heads.
+	 *
+	 * Reading, writing or deleting references must consistently go either
+	 * through the filesystem (special refs) or through the reference
+	 * backend (normal ones).
+	 */
+	static const char * const special_refs[] = {
+		"FETCH_HEAD",
+		"MERGE_HEAD",
+	};
+	size_t i;
+
+	for (i = 0; i < ARRAY_SIZE(special_refs); i++)
+		if (!strcmp(refname, special_refs[i]))
+			return 1;
+
+	return 0;
+}
+
 int refs_read_raw_ref(struct ref_store *ref_store, const char *refname,
 		      struct object_id *oid, struct strbuf *referent,
 		      unsigned int *type, int *failure_errno)
 {
 	assert(failure_errno);
-	if (!strcmp(refname, "FETCH_HEAD") || !strcmp(refname, "MERGE_HEAD")) {
+	if (is_special_ref(refname))
 		return refs_read_special_head(ref_store, refname, oid, referent,
 					      type, failure_errno);
-	}
 
 	return ref_store->be->read_raw_ref(ref_store, refname, oid, referent,
 					   type, failure_errno);
@@ -1928,11 +1976,9 @@ const char *refs_resolve_ref_unsafe(struct ref_store *refs,
 }
 
 /* backend functions */
-int refs_init_db(struct strbuf *err)
+int refs_init_db(struct ref_store *refs, int flags, struct strbuf *err)
 {
-	struct ref_store *refs = get_main_ref_store(the_repository);
-
-	return refs->be->init_db(refs, err);
+	return refs->be->init_db(refs, flags, err);
 }
 
 const char *resolve_ref_unsafe(const char *refname, int resolve_flags,
@@ -2029,12 +2075,12 @@ static struct ref_store *ref_store_init(struct repository *repo,
 					const char *gitdir,
 					unsigned int flags)
 {
-	const char *be_name = "files";
-	struct ref_storage_be *be = find_ref_storage_backend(be_name);
+	const struct ref_storage_be *be;
 	struct ref_store *refs;
 
+	be = find_ref_storage_backend(repo->ref_storage_format);
 	if (!be)
-		BUG("reference backend %s is unknown", be_name);
+		BUG("reference backend is unknown");
 
 	refs = be->init(repo, gitdir, flags);
 	return refs;
@@ -2599,13 +2645,55 @@ void ref_transaction_for_each_queued_update(struct ref_transaction *transaction,
 int refs_delete_refs(struct ref_store *refs, const char *logmsg,
 		     struct string_list *refnames, unsigned int flags)
 {
+	struct ref_transaction *transaction;
+	struct strbuf err = STRBUF_INIT;
+	struct string_list_item *item;
+	int ret = 0, failures = 0;
 	char *msg;
-	int retval;
+
+	if (!refnames->nr)
+		return 0;
 
 	msg = normalize_reflog_message(logmsg);
-	retval = refs->be->delete_refs(refs, msg, refnames, flags);
+
+	/*
+	 * Since we don't check the references' old_oids, the
+	 * individual updates can't fail, so we can pack all of the
+	 * updates into a single transaction.
+	 */
+	transaction = ref_store_transaction_begin(refs, &err);
+	if (!transaction) {
+		ret = error("%s", err.buf);
+		goto out;
+	}
+
+	for_each_string_list_item(item, refnames) {
+		ret = ref_transaction_delete(transaction, item->string,
+					     NULL, flags, msg, &err);
+		if (ret) {
+			warning(_("could not delete reference %s: %s"),
+				item->string, err.buf);
+			strbuf_reset(&err);
+			failures = 1;
+		}
+	}
+
+	ret = ref_transaction_commit(transaction, &err);
+	if (ret) {
+		if (refnames->nr == 1)
+			error(_("could not delete reference %s: %s"),
+			      refnames->items[0].string, err.buf);
+		else
+			error(_("could not delete references: %s"), err.buf);
+	}
+
+out:
+	if (!ret && failures)
+		ret = -1;
+	ref_transaction_free(transaction);
+	strbuf_release(&err);
 	free(msg);
-	return retval;
+	return ret;
 }
 
 int delete_refs(const char *msg, struct string_list *refnames,
diff --git a/refs.h b/refs.h
index ff113bb..303c5fa 100644
--- a/refs.h
+++ b/refs.h
@@ -11,6 +11,9 @@ struct string_list;
 struct string_list_item;
 struct worktree;
 
+unsigned int ref_storage_format_by_name(const char *name);
+const char *ref_storage_format_to_name(unsigned int ref_storage_format);
+
 /*
  * Resolve a reference, recursively following symbolic refererences.
  *
@@ -123,7 +126,9 @@ int should_autocreate_reflog(const char *refname);
 
 int is_branch(const char *refname);
 
-int refs_init_db(struct strbuf *err);
+#define REFS_INIT_DB_IS_WORKTREE (1 << 0)
+
+int refs_init_db(struct ref_store *refs, int flags, struct strbuf *err);
 
 /*
  * Return the peeled value of the oid currently being iterated via
diff --git a/refs/debug.c b/refs/debug.c
index b7ffc4c..634681c 100644
--- a/refs/debug.c
+++ b/refs/debug.c
@@ -33,10 +33,10 @@ struct ref_store *maybe_debug_wrap_ref_store(const char *gitdir, struct ref_stor
 	return (struct ref_store *)res;
 }
 
-static int debug_init_db(struct ref_store *refs, struct strbuf *err)
+static int debug_init_db(struct ref_store *refs, int flags, struct strbuf *err)
 {
 	struct debug_ref_store *drefs = (struct debug_ref_store *)refs;
-	int res = drefs->refs->be->init_db(drefs->refs, err);
+	int res = drefs->refs->be->init_db(drefs->refs, flags, err);
 	trace_printf_key(&trace_refs, "init_db: %d\n", res);
 	return res;
 }
@@ -143,20 +143,6 @@ static int debug_create_symref(struct ref_store *ref_store,
 	return res;
 }
 
-static int debug_delete_refs(struct ref_store *ref_store, const char *msg,
-			     struct string_list *refnames, unsigned int flags)
-{
-	struct debug_ref_store *drefs = (struct debug_ref_store *)ref_store;
-	int res =
-		drefs->refs->be->delete_refs(drefs->refs, msg, refnames, flags);
-	int i;
-	trace_printf_key(&trace_refs, "delete_refs {\n");
-	for (i = 0; i < refnames->nr; i++)
-		trace_printf_key(&trace_refs, "%s\n", refnames->items[i].string);
-	trace_printf_key(&trace_refs, "}: %d\n", res);
-	return res;
-}
-
 static int debug_rename_ref(struct ref_store *ref_store, const char *oldref,
 			    const char *newref, const char *logmsg)
 {
@@ -440,7 +426,6 @@ static int debug_reflog_expire(struct ref_store *ref_store, const char *refname,
 }
 
 struct ref_storage_be refs_be_debug = {
-	.next = NULL,
 	.name = "debug",
 	.init = NULL,
 	.init_db = debug_init_db,
@@ -458,7 +443,6 @@ struct ref_storage_be refs_be_debug = {
 
 	.pack_refs = debug_pack_refs,
 	.create_symref = debug_create_symref,
-	.delete_refs = debug_delete_refs,
 	.rename_ref = debug_rename_ref,
 	.copy_ref = debug_copy_ref,
 
diff --git a/refs/files-backend.c b/refs/files-backend.c
index 922e65e..75dcc21 100644
--- a/refs/files-backend.c
+++ b/refs/files-backend.c
@@ -1263,54 +1263,6 @@ static int files_pack_refs(struct ref_store *ref_store,
 	return 0;
 }
 
-static int files_delete_refs(struct ref_store *ref_store, const char *msg,
-			     struct string_list *refnames, unsigned int flags)
-{
-	struct files_ref_store *refs =
-		files_downcast(ref_store, REF_STORE_WRITE, "delete_refs");
-	struct strbuf err = STRBUF_INIT;
-	int i, result = 0;
-
-	if (!refnames->nr)
-		return 0;
-
-	if (packed_refs_lock(refs->packed_ref_store, 0, &err))
-		goto error;
-
-	if (refs_delete_refs(refs->packed_ref_store, msg, refnames, flags)) {
-		packed_refs_unlock(refs->packed_ref_store);
-		goto error;
-	}
-
-	packed_refs_unlock(refs->packed_ref_store);
-
-	for (i = 0; i < refnames->nr; i++) {
-		const char *refname = refnames->items[i].string;
-
-		if (refs_delete_ref(&refs->base, msg, refname, NULL, flags))
-			result |= error(_("could not remove reference %s"), refname);
-	}
-
-	strbuf_release(&err);
-	return result;
-
-error:
-	/*
-	 * If we failed to rewrite the packed-refs file, then it is
-	 * unsafe to try to remove loose refs, because doing so might
-	 * expose an obsolete packed value for a reference that might
-	 * even point at an object that has been garbage collected.
-	 */
-	if (refnames->nr == 1)
-		error(_("could not delete reference %s: %s"),
-		      refnames->items[0].string, err.buf);
-	else
-		error(_("could not delete references: %s"), err.buf);
-
-	strbuf_release(&err);
-	return -1;
-}
-
 /*
  * People using contrib's git-new-workdir have .git/logs/refs ->
  * /some/other/path/.git/logs/refs, and that may live on another device.
@@ -3266,28 +3218,52 @@ static int files_reflog_expire(struct ref_store *ref_store,
 	return -1;
 }
 
-static int files_init_db(struct ref_store *ref_store, struct strbuf *err UNUSED)
+static int files_init_db(struct ref_store *ref_store,
+			 int flags,
+			 struct strbuf *err UNUSED)
 {
 	struct files_ref_store *refs =
 		files_downcast(ref_store, REF_STORE_WRITE, "init_db");
 	struct strbuf sb = STRBUF_INIT;
 
 	/*
-	 * Create .git/refs/{heads,tags}
+	 * We need to create a "refs" dir in any case so that older versions of
+	 * Git can tell that this is a repository. This serves two main purposes:
+	 *
+	 * - Clients will know to stop walking the parent-directory chain when
+	 *   detecting the Git repository. Otherwise they may end up detecting
+	 *   a Git repository in a parent directory instead.
+	 *
+	 * - Instead of failing to detect a repository with unknown reference
+	 *   format altogether, old clients will print an error saying that
+	 *   they do not understand the reference format extension.
 	 */
-	files_ref_path(refs, &sb, "refs/heads");
+	strbuf_addf(&sb, "%s/refs", ref_store->gitdir);
 	safe_create_dir(sb.buf, 1);
+	adjust_shared_perm(sb.buf);
 
-	strbuf_reset(&sb);
-	files_ref_path(refs, &sb, "refs/tags");
-	safe_create_dir(sb.buf, 1);
+	/*
+	 * There is no need to create directories for common refs when creating
+	 * a worktree ref store.
+	 */
+	if (!(flags & REFS_INIT_DB_IS_WORKTREE)) {
+		/*
+		 * Create .git/refs/{heads,tags}
+		 */
+		strbuf_reset(&sb);
+		files_ref_path(refs, &sb, "refs/heads");
+		safe_create_dir(sb.buf, 1);
+
+		strbuf_reset(&sb);
+		files_ref_path(refs, &sb, "refs/tags");
+		safe_create_dir(sb.buf, 1);
+	}
 
 	strbuf_release(&sb);
 	return 0;
 }
 
 struct ref_storage_be refs_be_files = {
-	.next = NULL,
 	.name = "files",
 	.init = files_ref_store_create,
 	.init_db = files_init_db,
@@ -3298,7 +3274,6 @@ struct ref_storage_be refs_be_files = {
 
 	.pack_refs = files_pack_refs,
 	.create_symref = files_create_symref,
-	.delete_refs = files_delete_refs,
 	.rename_ref = files_rename_ref,
 	.copy_ref = files_copy_ref,
 
diff --git a/refs/packed-backend.c b/refs/packed-backend.c
index 5963e67..a499a91 100644
--- a/refs/packed-backend.c
+++ b/refs/packed-backend.c
@@ -1245,6 +1245,7 @@ static const char PACKED_REFS_HEADER[] =
 	"# pack-refs with: peeled fully-peeled sorted \n";
 
 static int packed_init_db(struct ref_store *ref_store UNUSED,
+			  int flags UNUSED,
 			  struct strbuf *err UNUSED)
 {
 	/* Nothing to do. */
@@ -1687,55 +1688,6 @@ static int packed_initial_transaction_commit(struct ref_store *ref_store UNUSED,
 	return ref_transaction_commit(transaction, err);
 }
 
-static int packed_delete_refs(struct ref_store *ref_store, const char *msg,
-			     struct string_list *refnames, unsigned int flags)
-{
-	struct packed_ref_store *refs =
-		packed_downcast(ref_store, REF_STORE_WRITE, "delete_refs");
-	struct strbuf err = STRBUF_INIT;
-	struct ref_transaction *transaction;
-	struct string_list_item *item;
-	int ret;
-
-	(void)refs; /* We need the check above, but don't use the variable */
-
-	if (!refnames->nr)
-		return 0;
-
-	/*
-	 * Since we don't check the references' old_oids, the
-	 * individual updates can't fail, so we can pack all of the
-	 * updates into a single transaction.
-	 */
-
-	transaction = ref_store_transaction_begin(ref_store, &err);
-	if (!transaction)
-		return -1;
-
-	for_each_string_list_item(item, refnames) {
-		if (ref_transaction_delete(transaction, item->string, NULL,
-					   flags, msg, &err)) {
-			warning(_("could not delete reference %s: %s"),
-				item->string, err.buf);
-			strbuf_reset(&err);
-		}
-	}
-
-	ret = ref_transaction_commit(transaction, &err);
-
-	if (ret) {
-		if (refnames->nr == 1)
-			error(_("could not delete reference %s: %s"),
-			      refnames->items[0].string, err.buf);
-		else
-			error(_("could not delete references: %s"), err.buf);
-	}
-
-	ref_transaction_free(transaction);
-	strbuf_release(&err);
-	return ret;
-}
-
 static int packed_pack_refs(struct ref_store *ref_store UNUSED,
 			    struct pack_refs_opts *pack_opts UNUSED)
 {
@@ -1753,7 +1705,6 @@ static struct ref_iterator *packed_reflog_iterator_begin(struct ref_store *ref_s
 }
 
 struct ref_storage_be refs_be_packed = {
-	.next = NULL,
 	.name = "packed",
 	.init = packed_ref_store_create,
 	.init_db = packed_init_db,
@@ -1764,7 +1715,6 @@ struct ref_storage_be refs_be_packed = {
 
 	.pack_refs = packed_pack_refs,
 	.create_symref = NULL,
-	.delete_refs = packed_delete_refs,
 	.rename_ref = NULL,
 	.copy_ref = NULL,
 
diff --git a/refs/refs-internal.h b/refs/refs-internal.h
index 9db8aec..8221982 100644
--- a/refs/refs-internal.h
+++ b/refs/refs-internal.h
@@ -529,7 +529,9 @@ typedef struct ref_store *ref_store_init_fn(struct repository *repo,
 					    const char *gitdir,
 					    unsigned int flags);
 
-typedef int ref_init_db_fn(struct ref_store *refs, struct strbuf *err);
+typedef int ref_init_db_fn(struct ref_store *refs,
+			   int flags,
+			   struct strbuf *err);
 
 typedef int ref_transaction_prepare_fn(struct ref_store *refs,
 				       struct ref_transaction *transaction,
@@ -553,8 +555,6 @@ typedef int create_symref_fn(struct ref_store *ref_store,
 			     const char *ref_target,
 			     const char *refs_heads_master,
 			     const char *logmsg);
-typedef int delete_refs_fn(struct ref_store *ref_store, const char *msg,
-			   struct string_list *refnames, unsigned int flags);
 typedef int rename_ref_fn(struct ref_store *ref_store,
 			  const char *oldref, const char *newref,
 			  const char *logmsg);
@@ -665,7 +665,6 @@ typedef int read_symbolic_ref_fn(struct ref_store *ref_store, const char *refnam
 				 struct strbuf *referent);
 
 struct ref_storage_be {
-	struct ref_storage_be *next;
 	const char *name;
 	ref_store_init_fn *init;
 	ref_init_db_fn *init_db;
@@ -677,7 +676,6 @@ struct ref_storage_be {
 
 	pack_refs_fn *pack_refs;
 	create_symref_fn *create_symref;
-	delete_refs_fn *delete_refs;
 	rename_ref_fn *rename_ref;
 	copy_ref_fn *copy_ref;
 
diff --git a/reftable/basics.c b/reftable/basics.c
index f761e48..0785aff 100644
--- a/reftable/basics.c
+++ b/reftable/basics.c
@@ -64,12 +64,11 @@ void free_names(char **a)
 	reftable_free(a);
 }
 
-int names_length(char **names)
+size_t names_length(char **names)
 {
 	char **p = names;
-	for (; *p; p++) {
-		/* empty */
-	}
+	while (*p)
+		p++;
 	return p - names;
 }
 
@@ -89,17 +88,13 @@ void parse_names(char *buf, int size, char ***namesp)
 			next = end;
 		}
 		if (p < next) {
-			if (names_len == names_cap) {
-				names_cap = 2 * names_cap + 1;
-				names = reftable_realloc(
-					names, names_cap * sizeof(*names));
-			}
+			REFTABLE_ALLOC_GROW(names, names_len + 1, names_cap);
 			names[names_len++] = xstrdup(p);
 		}
 		p = next + 1;
 	}
 
-	names = reftable_realloc(names, (names_len + 1) * sizeof(*names));
+	REFTABLE_REALLOC_ARRAY(names, names_len + 1);
 	names[names_len] = NULL;
 	*namesp = names;
 }
diff --git a/reftable/basics.h b/reftable/basics.h
index 096b368..91f3533 100644
--- a/reftable/basics.h
+++ b/reftable/basics.h
@@ -44,14 +44,27 @@ void parse_names(char *buf, int size, char ***namesp);
 int names_equal(char **a, char **b);
 
 /* returns the array size of a NULL-terminated array of strings. */
-int names_length(char **names);
+size_t names_length(char **names);
 
 /* Allocation routines; they invoke the functions set through
  * reftable_set_alloc() */
 void *reftable_malloc(size_t sz);
 void *reftable_realloc(void *p, size_t sz);
 void reftable_free(void *p);
-void *reftable_calloc(size_t sz);
+void *reftable_calloc(size_t nelem, size_t elsize);
+
+#define REFTABLE_ALLOC_ARRAY(x, alloc) (x) = reftable_malloc(st_mult(sizeof(*(x)), (alloc)))
+#define REFTABLE_CALLOC_ARRAY(x, alloc) (x) = reftable_calloc((alloc), sizeof(*(x)))
+#define REFTABLE_REALLOC_ARRAY(x, alloc) (x) = reftable_realloc((x), st_mult(sizeof(*(x)), (alloc)))
+#define REFTABLE_ALLOC_GROW(x, nr, alloc) \
+	do { \
+		if ((nr) > alloc) { \
+			alloc = 2 * (alloc) + 1; \
+			if (alloc < (nr)) \
+				alloc = (nr); \
+			REFTABLE_REALLOC_ARRAY(x, alloc); \
+		} \
+	} while (0)
 
 /* Find the longest shared prefix size of `a` and `b` */
 struct strbuf;
diff --git a/reftable/block.c b/reftable/block.c
index 1df3d8a..ce8a7d2 100644
--- a/reftable/block.c
+++ b/reftable/block.c
@@ -51,12 +51,7 @@ static int block_writer_register_restart(struct block_writer *w, int n,
 	if (2 + 3 * rlen + n > w->block_size - w->next)
 		return -1;
 	if (is_restart) {
-		if (w->restart_len == w->restart_cap) {
-			w->restart_cap = w->restart_cap * 2 + 1;
-			w->restarts = reftable_realloc(
-				w->restarts, sizeof(uint32_t) * w->restart_cap);
-		}
-
+		REFTABLE_ALLOC_GROW(w->restarts, w->restart_len + 1, w->restart_cap);
 		w->restarts[w->restart_len++] = w->next;
 	}
 
@@ -148,8 +143,10 @@ int block_writer_finish(struct block_writer *w)
 		int block_header_skip = 4 + w->header_off;
 		uLongf src_len = w->next - block_header_skip;
 		uLongf dest_cap = src_len * 1.001 + 12;
+		uint8_t *compressed;
 
-		uint8_t *compressed = reftable_malloc(dest_cap);
+		REFTABLE_ALLOC_ARRAY(compressed, dest_cap);
+
 		while (1) {
 			uLongf out_dest_len = dest_cap;
 			int zresult = compress2(compressed, &out_dest_len,
@@ -206,9 +203,9 @@ int block_reader_init(struct block_reader *br, struct reftable_block *block,
 		uLongf dst_len = sz - block_header_skip; /* total size of dest
 							    buffer. */
 		uLongf src_len = block->len - block_header_skip;
-		/* Log blocks specify the *uncompressed* size in their header.
-		 */
-		uncompressed = reftable_malloc(sz);
+
+		/* Log blocks specify the *uncompressed* size in their header. */
+		REFTABLE_ALLOC_ARRAY(uncompressed, sz);
 
 		/* Copy over the block header verbatim. It's not compressed. */
 		memcpy(uncompressed, block->data, block_header_skip);
@@ -385,23 +382,23 @@ int block_reader_seek(struct block_reader *br, struct block_iter *it,
 		.key = *want,
 		.r = br,
 	};
-	struct reftable_record rec = reftable_new_record(block_reader_type(br));
-	int err = 0;
 	struct block_iter next = BLOCK_ITER_INIT;
+	struct reftable_record rec;
+	int err = 0, i;
 
-	int i = binsearch(br->restart_count, &restart_key_less, &args);
 	if (args.error) {
 		err = REFTABLE_FORMAT_ERROR;
 		goto done;
 	}
 
-	it->br = br;
-	if (i > 0) {
-		i--;
-		it->next_off = block_reader_restart_offset(br, i);
-	} else {
+	i = binsearch(br->restart_count, &restart_key_less, &args);
+	if (i > 0)
+		it->next_off = block_reader_restart_offset(br, i - 1);
+	else
 		it->next_off = br->header_off + 4;
-	}
+	it->br = br;
+
+	reftable_record_init(&rec, block_reader_type(br));
 
 	/* We're looking for the last entry less/equal than the wanted key, so
 	   we have to go one entry too far and then back up.
diff --git a/reftable/block_test.c b/reftable/block_test.c
index c00bbc8..e162c6e 100644
--- a/reftable/block_test.c
+++ b/reftable/block_test.c
@@ -36,7 +36,7 @@ static void test_block_read_write(void)
 	int j = 0;
 	struct strbuf want = STRBUF_INIT;
 
-	block.data = reftable_calloc(block_size);
+	REFTABLE_CALLOC_ARRAY(block.data, block_size);
 	block.len = block_size;
 	block.source = malloc_block_source();
 	block_writer_init(&bw, BLOCK_TYPE_REF, block.data, block_size,
@@ -49,13 +49,11 @@ static void test_block_read_write(void)
 
 	for (i = 0; i < N; i++) {
 		char name[100];
-		uint8_t hash[GIT_SHA1_RAWSZ];
 		snprintf(name, sizeof(name), "branch%02d", i);
-		memset(hash, i, sizeof(hash));
 
 		rec.u.ref.refname = name;
 		rec.u.ref.value_type = REFTABLE_REF_VAL1;
-		rec.u.ref.value.val1 = hash;
+		memset(rec.u.ref.value.val1, i, GIT_SHA1_RAWSZ);
 
 		names[i] = xstrdup(name);
 		n = block_writer_add(&bw, &rec);
diff --git a/reftable/blocksource.c b/reftable/blocksource.c
index a1ea304..eeed254 100644
--- a/reftable/blocksource.c
+++ b/reftable/blocksource.c
@@ -29,7 +29,7 @@ static int strbuf_read_block(void *v, struct reftable_block *dest, uint64_t off,
 {
 	struct strbuf *b = v;
 	assert(off + size <= b->len);
-	dest->data = reftable_calloc(size);
+	REFTABLE_CALLOC_ARRAY(dest->data, size);
 	memcpy(dest->data, b->buf + off, size);
 	dest->len = size;
 	return size;
@@ -76,8 +76,8 @@ struct reftable_block_source malloc_block_source(void)
 }
 
 struct file_block_source {
-	int fd;
 	uint64_t size;
+	unsigned char *data;
 };
 
 static uint64_t file_size(void *b)
@@ -87,19 +87,12 @@ static uint64_t file_size(void *b)
 
 static void file_return_block(void *b, struct reftable_block *dest)
 {
-	if (dest->len)
-		memset(dest->data, 0xff, dest->len);
-	reftable_free(dest->data);
 }
 
-static void file_close(void *b)
+static void file_close(void *v)
 {
-	int fd = ((struct file_block_source *)b)->fd;
-	if (fd > 0) {
-		close(fd);
-		((struct file_block_source *)b)->fd = 0;
-	}
-
+	struct file_block_source *b = v;
+	munmap(b->data, b->size);
 	reftable_free(b);
 }
 
@@ -108,9 +101,7 @@ static int file_read_block(void *v, struct reftable_block *dest, uint64_t off,
 {
 	struct file_block_source *b = v;
 	assert(off + size <= b->size);
-	dest->data = reftable_malloc(size);
-	if (pread_in_full(b->fd, dest->data, size, off) != size)
-		return -1;
+	dest->data = b->data + off;
 	dest->len = size;
 	return size;
 }
@@ -125,26 +116,26 @@ static struct reftable_block_source_vtable file_vtable = {
 int reftable_block_source_from_file(struct reftable_block_source *bs,
 				    const char *name)
 {
-	struct stat st = { 0 };
-	int err = 0;
-	int fd = open(name, O_RDONLY);
-	struct file_block_source *p = NULL;
+	struct file_block_source *p;
+	struct stat st;
+	int fd;
+
+	fd = open(name, O_RDONLY);
 	if (fd < 0) {
-		if (errno == ENOENT) {
+		if (errno == ENOENT)
 			return REFTABLE_NOT_EXIST_ERROR;
-		}
 		return -1;
 	}
 
-	err = fstat(fd, &st);
-	if (err < 0) {
+	if (fstat(fd, &st) < 0) {
 		close(fd);
 		return REFTABLE_IO_ERROR;
 	}
 
-	p = reftable_calloc(sizeof(struct file_block_source));
+	REFTABLE_CALLOC_ARRAY(p, 1);
 	p->size = st.st_size;
-	p->fd = fd;
+	p->data = xmmap(NULL, st.st_size, PROT_READ, MAP_PRIVATE, fd, 0);
+	close(fd);
 
 	assert(!bs->ops);
 	bs->ops = &file_vtable;
diff --git a/reftable/iter.c b/reftable/iter.c
index a8d174c..8b5ebf6 100644
--- a/reftable/iter.c
+++ b/reftable/iter.c
@@ -160,8 +160,7 @@ int new_indexed_table_ref_iter(struct indexed_table_ref_iter **dest,
 			       int oid_len, uint64_t *offsets, int offset_len)
 {
 	struct indexed_table_ref_iter empty = INDEXED_TABLE_REF_ITER_INIT;
-	struct indexed_table_ref_iter *itr =
-		reftable_calloc(sizeof(struct indexed_table_ref_iter));
+	struct indexed_table_ref_iter *itr = reftable_calloc(1, sizeof(*itr));
 	int err = 0;
 
 	*itr = empty;
diff --git a/reftable/merged.c b/reftable/merged.c
index 5743940..a0f222e 100644
--- a/reftable/merged.c
+++ b/reftable/merged.c
@@ -19,24 +19,23 @@ license that can be found in the LICENSE file or at
 
 static int merged_iter_init(struct merged_iter *mi)
 {
-	int i = 0;
-	for (i = 0; i < mi->stack_len; i++) {
-		struct reftable_record rec = reftable_new_record(mi->typ);
-		int err = iterator_next(&mi->stack[i], &rec);
-		if (err < 0) {
-			return err;
-		}
+	for (size_t i = 0; i < mi->stack_len; i++) {
+		struct pq_entry e = {
+			.index = i,
+		};
+		int err;
 
+		reftable_record_init(&e.rec, mi->typ);
+		err = iterator_next(&mi->stack[i], &e.rec);
+		if (err < 0)
+			return err;
 		if (err > 0) {
 			reftable_iterator_destroy(&mi->stack[i]);
-			reftable_record_release(&rec);
-		} else {
-			struct pq_entry e = {
-				.rec = rec,
-				.index = i,
-			};
-			merged_iter_pqueue_add(&mi->pq, &e);
+			reftable_record_release(&e.rec);
+			continue;
 		}
+
+		merged_iter_pqueue_add(&mi->pq, &e);
 	}
 
 	return 0;
@@ -45,11 +44,10 @@ static int merged_iter_init(struct merged_iter *mi)
 static void merged_iter_close(void *p)
 {
 	struct merged_iter *mi = p;
-	int i = 0;
+
 	merged_iter_pqueue_release(&mi->pq);
-	for (i = 0; i < mi->stack_len; i++) {
+	for (size_t i = 0; i < mi->stack_len; i++)
 		reftable_iterator_destroy(&mi->stack[i]);
-	}
 	reftable_free(mi->stack);
 	strbuf_release(&mi->key);
 	strbuf_release(&mi->entry_key);
@@ -59,10 +57,12 @@ static int merged_iter_advance_nonnull_subiter(struct merged_iter *mi,
 					       size_t idx)
 {
 	struct pq_entry e = {
-		.rec = reftable_new_record(mi->typ),
 		.index = idx,
 	};
-	int err = iterator_next(&mi->stack[idx], &e.rec);
+	int err;
+
+	reftable_record_init(&e.rec, mi->typ);
+	err = iterator_next(&mi->stack[idx], &e.rec);
 	if (err < 0)
 		return err;
 
@@ -123,12 +123,12 @@ static int merged_iter_next_entry(struct merged_iter *mi,
 		reftable_record_release(&top.rec);
 	}
 
-	reftable_record_copy_from(rec, &entry.rec, hash_size(mi->hash_id));
+	reftable_record_release(rec);
+	*rec = entry.rec;
 
 done:
-	reftable_record_release(&entry.rec);
-	strbuf_release(&mi->entry_key);
-	strbuf_release(&mi->key);
+	if (err)
+		reftable_record_release(&entry.rec);
 	return err;
 }
 
@@ -168,14 +168,14 @@ static void iterator_from_merged_iter(struct reftable_iterator *it,
 }
 
 int reftable_new_merged_table(struct reftable_merged_table **dest,
-			      struct reftable_table *stack, int n,
+			      struct reftable_table *stack, size_t n,
 			      uint32_t hash_id)
 {
 	struct reftable_merged_table *m = NULL;
 	uint64_t last_max = 0;
 	uint64_t first_min = 0;
-	int i = 0;
-	for (i = 0; i < n; i++) {
+
+	for (size_t i = 0; i < n; i++) {
 		uint64_t min = reftable_table_min_update_index(&stack[i]);
 		uint64_t max = reftable_table_max_update_index(&stack[i]);
 
@@ -190,7 +190,7 @@ int reftable_new_merged_table(struct reftable_merged_table **dest,
 		}
 	}
 
-	m = reftable_calloc(sizeof(struct reftable_merged_table));
+	REFTABLE_CALLOC_ARRAY(m, 1);
 	m->stack = stack;
 	m->stack_len = n;
 	m->min = first_min;
@@ -239,50 +239,38 @@ static int merged_table_seek_record(struct reftable_merged_table *mt,
 				    struct reftable_iterator *it,
 				    struct reftable_record *rec)
 {
-	struct reftable_iterator *iters = reftable_calloc(
-		sizeof(struct reftable_iterator) * mt->stack_len);
 	struct merged_iter merged = {
-		.stack = iters,
 		.typ = reftable_record_type(rec),
 		.hash_id = mt->hash_id,
 		.suppress_deletions = mt->suppress_deletions,
 		.key = STRBUF_INIT,
 		.entry_key = STRBUF_INIT,
 	};
-	int n = 0;
-	int err = 0;
-	int i = 0;
-	for (i = 0; i < mt->stack_len && err == 0; i++) {
-		int e = reftable_table_seek_record(&mt->stack[i], &iters[n],
-						   rec);
-		if (e < 0) {
-			err = e;
-		}
-		if (e == 0) {
-			n++;
-		}
-	}
-	if (err < 0) {
-		int i = 0;
-		for (i = 0; i < n; i++) {
-			reftable_iterator_destroy(&iters[i]);
-		}
-		reftable_free(iters);
-		return err;
+	struct merged_iter *p;
+	int err;
+
+	REFTABLE_CALLOC_ARRAY(merged.stack, mt->stack_len);
+	for (size_t i = 0; i < mt->stack_len; i++) {
+		err = reftable_table_seek_record(&mt->stack[i],
+						 &merged.stack[merged.stack_len], rec);
+		if (err < 0)
+			goto out;
+		if (!err)
+			merged.stack_len++;
 	}
 
-	merged.stack_len = n;
 	err = merged_iter_init(&merged);
-	if (err < 0) {
+	if (err < 0)
+		goto out;
+
+	p = reftable_malloc(sizeof(struct merged_iter));
+	*p = merged;
+	iterator_from_merged_iter(it, p);
+
+out:
+	if (err < 0)
 		merged_iter_close(&merged);
-		return err;
-	} else {
-		struct merged_iter *p =
-			reftable_malloc(sizeof(struct merged_iter));
-		*p = merged;
-		iterator_from_merged_iter(it, p);
-	}
-	return 0;
+	return err;
 }
 
 int reftable_merged_table_seek_ref(struct reftable_merged_table *mt,
diff --git a/reftable/merged_test.c b/reftable/merged_test.c
index 0d6e0d4..d0f77a3 100644
--- a/reftable/merged_test.c
+++ b/reftable/merged_test.c
@@ -42,7 +42,7 @@ static void write_test_table(struct strbuf *buf,
 		}
 	}
 
-	w = reftable_new_writer(&strbuf_add_void, buf, &opts);
+	w = reftable_new_writer(&strbuf_add_void, &noop_flush, buf, &opts);
 	reftable_writer_set_limits(w, min, max);
 
 	for (i = 0; i < n; i++) {
@@ -70,7 +70,7 @@ static void write_test_log_table(struct strbuf *buf,
 		.exact_log_message = 1,
 	};
 	struct reftable_writer *w = NULL;
-	w = reftable_new_writer(&strbuf_add_void, buf, &opts);
+	w = reftable_new_writer(&strbuf_add_void, &noop_flush, buf, &opts);
 	reftable_writer_set_limits(w, update_index, update_index);
 
 	for (i = 0; i < n; i++) {
@@ -88,16 +88,17 @@ static struct reftable_merged_table *
 merged_table_from_records(struct reftable_ref_record **refs,
 			  struct reftable_block_source **source,
 			  struct reftable_reader ***readers, int *sizes,
-			  struct strbuf *buf, int n)
+			  struct strbuf *buf, size_t n)
 {
-	int i = 0;
 	struct reftable_merged_table *mt = NULL;
+	struct reftable_table *tabs;
 	int err;
-	struct reftable_table *tabs =
-		reftable_calloc(n * sizeof(struct reftable_table));
-	*readers = reftable_calloc(n * sizeof(struct reftable_reader *));
-	*source = reftable_calloc(n * sizeof(**source));
-	for (i = 0; i < n; i++) {
+
+	REFTABLE_CALLOC_ARRAY(tabs, n);
+	REFTABLE_CALLOC_ARRAY(*readers, n);
+	REFTABLE_CALLOC_ARRAY(*source, n);
+
+	for (size_t i = 0; i < n; i++) {
 		write_test_table(&buf[i], refs[i], sizes[i]);
 		block_source_from_strbuf(&(*source)[i], &buf[i]);
 
@@ -122,13 +123,11 @@ static void readers_destroy(struct reftable_reader **readers, size_t n)
 
 static void test_merged_between(void)
 {
-	uint8_t hash1[GIT_SHA1_RAWSZ] = { 1, 2, 3, 0 };
-
 	struct reftable_ref_record r1[] = { {
 		.refname = "b",
 		.update_index = 1,
 		.value_type = REFTABLE_REF_VAL1,
-		.value.val1 = hash1,
+		.value.val1 = { 1, 2, 3, 0 },
 	} };
 	struct reftable_ref_record r2[] = { {
 		.refname = "a",
@@ -164,26 +163,24 @@ static void test_merged_between(void)
 
 static void test_merged(void)
 {
-	uint8_t hash1[GIT_SHA1_RAWSZ] = { 1 };
-	uint8_t hash2[GIT_SHA1_RAWSZ] = { 2 };
 	struct reftable_ref_record r1[] = {
 		{
 			.refname = "a",
 			.update_index = 1,
 			.value_type = REFTABLE_REF_VAL1,
-			.value.val1 = hash1,
+			.value.val1 = { 1 },
 		},
 		{
 			.refname = "b",
 			.update_index = 1,
 			.value_type = REFTABLE_REF_VAL1,
-			.value.val1 = hash1,
+			.value.val1 = { 1 },
 		},
 		{
 			.refname = "c",
 			.update_index = 1,
 			.value_type = REFTABLE_REF_VAL1,
-			.value.val1 = hash1,
+			.value.val1 = { 1 },
 		}
 	};
 	struct reftable_ref_record r2[] = { {
@@ -196,13 +193,13 @@ static void test_merged(void)
 			.refname = "c",
 			.update_index = 3,
 			.value_type = REFTABLE_REF_VAL1,
-			.value.val1 = hash2,
+			.value.val1 = { 2 },
 		},
 		{
 			.refname = "d",
 			.update_index = 3,
 			.value_type = REFTABLE_REF_VAL1,
-			.value.val1 = hash1,
+			.value.val1 = { 1 },
 		},
 	};
 
@@ -235,14 +232,10 @@ static void test_merged(void)
 	while (len < 100) { /* cap loops/recursion. */
 		struct reftable_ref_record ref = { NULL };
 		int err = reftable_iterator_next_ref(&it, &ref);
-		if (err > 0) {
+		if (err > 0)
 			break;
-		}
-		if (len == cap) {
-			cap = 2 * cap + 1;
-			out = reftable_realloc(
-				out, sizeof(struct reftable_ref_record) * cap);
-		}
+
+		REFTABLE_ALLOC_GROW(out, len + 1, cap);
 		out[len++] = ref;
 	}
 	reftable_iterator_destroy(&it);
@@ -269,16 +262,17 @@ static struct reftable_merged_table *
 merged_table_from_log_records(struct reftable_log_record **logs,
 			      struct reftable_block_source **source,
 			      struct reftable_reader ***readers, int *sizes,
-			      struct strbuf *buf, int n)
+			      struct strbuf *buf, size_t n)
 {
-	int i = 0;
 	struct reftable_merged_table *mt = NULL;
+	struct reftable_table *tabs;
 	int err;
-	struct reftable_table *tabs =
-		reftable_calloc(n * sizeof(struct reftable_table));
-	*readers = reftable_calloc(n * sizeof(struct reftable_reader *));
-	*source = reftable_calloc(n * sizeof(**source));
-	for (i = 0; i < n; i++) {
+
+	REFTABLE_CALLOC_ARRAY(tabs, n);
+	REFTABLE_CALLOC_ARRAY(*readers, n);
+	REFTABLE_CALLOC_ARRAY(*source, n);
+
+	for (size_t i = 0; i < n; i++) {
 		write_test_log_table(&buf[i], logs[i], sizes[i], i + 1);
 		block_source_from_strbuf(&(*source)[i], &buf[i]);
 
@@ -372,14 +366,10 @@ static void test_merged_logs(void)
 	while (len < 100) { /* cap loops/recursion. */
 		struct reftable_log_record log = { NULL };
 		int err = reftable_iterator_next_log(&it, &log);
-		if (err > 0) {
+		if (err > 0)
 			break;
-		}
-		if (len == cap) {
-			cap = 2 * cap + 1;
-			out = reftable_realloc(
-				out, sizeof(struct reftable_log_record) * cap);
-		}
+
+		REFTABLE_ALLOC_GROW(out, len + 1, cap);
 		out[len++] = log;
 	}
 	reftable_iterator_destroy(&it);
@@ -416,7 +406,7 @@ static void test_default_write_opts(void)
 	struct reftable_write_options opts = { 0 };
 	struct strbuf buf = STRBUF_INIT;
 	struct reftable_writer *w =
-		reftable_new_writer(&strbuf_add_void, &buf, &opts);
+		reftable_new_writer(&strbuf_add_void, &noop_flush, &buf, &opts);
 
 	struct reftable_ref_record rec = {
 		.refname = "master",
@@ -424,7 +414,7 @@ static void test_default_write_opts(void)
 	};
 	int err;
 	struct reftable_block_source source = { NULL };
-	struct reftable_table *tab = reftable_calloc(sizeof(*tab) * 1);
+	struct reftable_table *tab = reftable_calloc(1, sizeof(*tab));
 	uint32_t hash_id;
 	struct reftable_reader *rd = NULL;
 	struct reftable_merged_table *merged = NULL;
diff --git a/reftable/pq.c b/reftable/pq.c
index dcefeb7..2461daf 100644
--- a/reftable/pq.c
+++ b/reftable/pq.c
@@ -75,13 +75,9 @@ void merged_iter_pqueue_add(struct merged_iter_pqueue *pq, const struct pq_entry
 {
 	int i = 0;
 
-	if (pq->len == pq->cap) {
-		pq->cap = 2 * pq->cap + 1;
-		pq->heap = reftable_realloc(pq->heap,
-					    pq->cap * sizeof(struct pq_entry));
-	}
-
+	REFTABLE_ALLOC_GROW(pq->heap, pq->len + 1, pq->cap);
 	pq->heap[pq->len++] = *e;
+
 	i = pq->len - 1;
 	while (i > 0) {
 		int j = (i - 1) / 2;
diff --git a/reftable/publicbasics.c b/reftable/publicbasics.c
index bcb8253..44b84a1 100644
--- a/reftable/publicbasics.c
+++ b/reftable/publicbasics.c
@@ -37,8 +37,9 @@ void reftable_free(void *p)
 		free(p);
 }
 
-void *reftable_calloc(size_t sz)
+void *reftable_calloc(size_t nelem, size_t elsize)
 {
+	size_t sz = st_mult(nelem, elsize);
 	void *p = reftable_malloc(sz);
 	memset(p, 0, sz);
 	return p;
diff --git a/reftable/reader.c b/reftable/reader.c
index 64dc366..2663b03 100644
--- a/reftable/reader.c
+++ b/reftable/reader.c
@@ -444,13 +444,13 @@ static int reader_start(struct reftable_reader *r, struct table_iter *ti,
 static int reader_seek_linear(struct table_iter *ti,
 			      struct reftable_record *want)
 {
-	struct reftable_record rec =
-		reftable_new_record(reftable_record_type(want));
 	struct strbuf want_key = STRBUF_INIT;
 	struct strbuf got_key = STRBUF_INIT;
 	struct table_iter next = TABLE_ITER_INIT;
+	struct reftable_record rec;
 	int err = -1;
 
+	reftable_record_init(&rec, reftable_record_type(want));
 	reftable_record_key(want, &want_key);
 
 	while (1) {
@@ -508,8 +508,38 @@ static int reader_seek_indexed(struct reftable_reader *r,
 	if (err < 0)
 		goto done;
 
+	/*
+	 * The index may consist of multiple levels, where each level may have
+	 * multiple index blocks. We start by doing a linear search in the
+	 * highest layer that identifies the relevant index block as well as
+	 * the record inside that block that corresponds to our wanted key.
+	 */
 	err = reader_seek_linear(&index_iter, &want_index);
+	if (err < 0)
+		goto done;
+
+	/*
+	 * Traverse down the levels until we find a non-index entry.
+	 */
 	while (1) {
+		/*
+		 * In case we seek a record that does not exist the index iter
+		 * will tell us that the iterator is over. This works because
+		 * the last index entry of the current level will contain the
+		 * last key it knows about. So in case our seeked key is larger
+		 * than the last indexed key we know that it won't exist.
+		 *
+		 * There is one subtlety in the layout of the index section
+		 * that makes this work as expected: the highest-level index is
+		 * at end of the section and will point backwards and thus we
+		 * start reading from the end of the index section, not the
+		 * beginning.
+		 *
+		 * If that wasn't the case and the order was reversed then the
+		 * linear seek would seek into the lower levels and traverse
+		 * all levels of the index only to find out that the key does
+		 * not exist.
+		 */
 		err = table_iter_next(&index_iter, &index_result);
 		table_iter_block_done(&index_iter);
 		if (err != 0)
@@ -539,8 +569,7 @@ static int reader_seek_indexed(struct reftable_reader *r,
 
 	if (err == 0) {
 		struct table_iter empty = TABLE_ITER_INIT;
-		struct table_iter *malloced =
-			reftable_calloc(sizeof(struct table_iter));
+		struct table_iter *malloced = reftable_calloc(1, sizeof(*malloced));
 		*malloced = empty;
 		table_iter_copy_from(malloced, &next);
 		iterator_from_table_iter(it, malloced);
@@ -635,8 +664,7 @@ void reader_close(struct reftable_reader *r)
 int reftable_new_reader(struct reftable_reader **p,
 			struct reftable_block_source *src, char const *name)
 {
-	struct reftable_reader *rd =
-		reftable_calloc(sizeof(struct reftable_reader));
+	struct reftable_reader *rd = reftable_calloc(1, sizeof(*rd));
 	int err = init_reader(rd, src, name);
 	if (err == 0) {
 		*p = rd;
@@ -711,7 +739,7 @@ static int reftable_reader_refs_for_unindexed(struct reftable_reader *r,
 					      uint8_t *oid)
 {
 	struct table_iter ti_empty = TABLE_ITER_INIT;
-	struct table_iter *ti = reftable_calloc(sizeof(struct table_iter));
+	struct table_iter *ti = reftable_calloc(1, sizeof(*ti));
 	struct filtering_ref_iterator *filter = NULL;
 	struct filtering_ref_iterator empty = FILTERING_REF_ITERATOR_INIT;
 	int oid_len = hash_size(r->hash_id);
diff --git a/reftable/readwrite_test.c b/reftable/readwrite_test.c
index 79cd4e4..363fe0f 100644
--- a/reftable/readwrite_test.c
+++ b/reftable/readwrite_test.c
@@ -51,26 +51,25 @@ static void write_table(char ***names, struct strbuf *buf, int N,
 		.hash_id = hash_id,
 	};
 	struct reftable_writer *w =
-		reftable_new_writer(&strbuf_add_void, buf, &opts);
+		reftable_new_writer(&strbuf_add_void, &noop_flush, buf, &opts);
 	struct reftable_ref_record ref = { NULL };
 	int i = 0, n;
 	struct reftable_log_record log = { NULL };
 	const struct reftable_stats *stats = NULL;
-	*names = reftable_calloc(sizeof(char *) * (N + 1));
+
+	REFTABLE_CALLOC_ARRAY(*names, N + 1);
+
 	reftable_writer_set_limits(w, update_index, update_index);
 	for (i = 0; i < N; i++) {
-		uint8_t hash[GIT_SHA256_RAWSZ] = { 0 };
 		char name[100];
 		int n;
 
-		set_test_hash(hash, i);
-
 		snprintf(name, sizeof(name), "refs/heads/branch%02d", i);
 
 		ref.refname = name;
 		ref.update_index = update_index;
 		ref.value_type = REFTABLE_REF_VAL1;
-		ref.value.val1 = hash;
+		set_test_hash(ref.value.val1, i);
 		(*names)[i] = xstrdup(name);
 
 		n = reftable_writer_add_ref(w, &ref);
@@ -133,7 +132,7 @@ static void test_log_buffer_size(void)
 					   .message = "commit: 9\n",
 				   } } };
 	struct reftable_writer *w =
-		reftable_new_writer(&strbuf_add_void, &buf, &opts);
+		reftable_new_writer(&strbuf_add_void, &noop_flush, &buf, &opts);
 
 	/* This tests buffer extension for log compression. Must use a random
 	   hash, to ensure that the compressed part is larger than the original.
@@ -174,7 +173,7 @@ static void test_log_overflow(void)
 					   .message = msg,
 				   } } };
 	struct reftable_writer *w =
-		reftable_new_writer(&strbuf_add_void, &buf, &opts);
+		reftable_new_writer(&strbuf_add_void, &noop_flush, &buf, &opts);
 
 	uint8_t hash1[GIT_SHA1_RAWSZ]  = {1}, hash2[GIT_SHA1_RAWSZ] = { 2 };
 
@@ -191,7 +190,7 @@ static void test_log_overflow(void)
 static void test_log_write_read(void)
 {
 	int N = 2;
-	char **names = reftable_calloc(sizeof(char *) * (N + 1));
+	char **names = reftable_calloc(N + 1, sizeof(*names));
 	int err;
 	struct reftable_write_options opts = {
 		.block_size = 256,
@@ -205,7 +204,7 @@ static void test_log_write_read(void)
 	struct reftable_block_source source = { NULL };
 	struct strbuf buf = STRBUF_INIT;
 	struct reftable_writer *w =
-		reftable_new_writer(&strbuf_add_void, &buf, &opts);
+		reftable_new_writer(&strbuf_add_void, &noop_flush, &buf, &opts);
 	const struct reftable_stats *stats = NULL;
 	reftable_writer_set_limits(w, 0, N);
 	for (i = 0; i < N; i++) {
@@ -297,7 +296,7 @@ static void test_log_zlib_corruption(void)
 	struct reftable_block_source source = { 0 };
 	struct strbuf buf = STRBUF_INIT;
 	struct reftable_writer *w =
-		reftable_new_writer(&strbuf_add_void, &buf, &opts);
+		reftable_new_writer(&strbuf_add_void, &noop_flush, &buf, &opts);
 	const struct reftable_stats *stats = NULL;
 	uint8_t hash1[GIT_SHA1_RAWSZ] = { 1 };
 	uint8_t hash2[GIT_SHA1_RAWSZ] = { 2 };
@@ -522,7 +521,7 @@ static void test_table_read_write_seek_index(void)
 static void test_table_refs_for(int indexed)
 {
 	int N = 50;
-	char **want_names = reftable_calloc(sizeof(char *) * (N + 1));
+	char **want_names = reftable_calloc(N + 1, sizeof(*want_names));
 	int want_names_len = 0;
 	uint8_t want_hash[GIT_SHA1_RAWSZ];
 
@@ -538,7 +537,7 @@ static void test_table_refs_for(int indexed)
 
 	struct strbuf buf = STRBUF_INIT;
 	struct reftable_writer *w =
-		reftable_new_writer(&strbuf_add_void, &buf, &opts);
+		reftable_new_writer(&strbuf_add_void, &noop_flush, &buf, &opts);
 
 	struct reftable_iterator it = { NULL };
 	int j;
@@ -549,8 +548,6 @@ static void test_table_refs_for(int indexed)
 		uint8_t hash[GIT_SHA1_RAWSZ];
 		char fill[51] = { 0 };
 		char name[100];
-		uint8_t hash1[GIT_SHA1_RAWSZ];
-		uint8_t hash2[GIT_SHA1_RAWSZ];
 		struct reftable_ref_record ref = { NULL };
 
 		memset(hash, i, sizeof(hash));
@@ -560,11 +557,9 @@ static void test_table_refs_for(int indexed)
 		name[40] = 0;
 		ref.refname = name;
 
-		set_test_hash(hash1, i / 4);
-		set_test_hash(hash2, 3 + i / 4);
 		ref.value_type = REFTABLE_REF_VAL2;
-		ref.value.val2.value = hash1;
-		ref.value.val2.target_value = hash2;
+		set_test_hash(ref.value.val2.value, i / 4);
+		set_test_hash(ref.value.val2.target_value, 3 + i / 4);
 
 		/* 80 bytes / entry, so 3 entries per block. Yields 17
 		 */
@@ -572,8 +567,8 @@ static void test_table_refs_for(int indexed)
 		n = reftable_writer_add_ref(w, &ref);
 		EXPECT(n == 0);
 
-		if (!memcmp(hash1, want_hash, GIT_SHA1_RAWSZ) ||
-		    !memcmp(hash2, want_hash, GIT_SHA1_RAWSZ)) {
+		if (!memcmp(ref.value.val2.value, want_hash, GIT_SHA1_RAWSZ) ||
+		    !memcmp(ref.value.val2.target_value, want_hash, GIT_SHA1_RAWSZ)) {
 			want_names[want_names_len++] = xstrdup(name);
 		}
 	}
@@ -635,7 +630,7 @@ static void test_write_empty_table(void)
 	struct reftable_write_options opts = { 0 };
 	struct strbuf buf = STRBUF_INIT;
 	struct reftable_writer *w =
-		reftable_new_writer(&strbuf_add_void, &buf, &opts);
+		reftable_new_writer(&strbuf_add_void, &noop_flush, &buf, &opts);
 	struct reftable_block_source source = { NULL };
 	struct reftable_reader *rd = NULL;
 	struct reftable_ref_record rec = { NULL };
@@ -673,12 +668,11 @@ static void test_write_object_id_min_length(void)
 	};
 	struct strbuf buf = STRBUF_INIT;
 	struct reftable_writer *w =
-		reftable_new_writer(&strbuf_add_void, &buf, &opts);
-	uint8_t hash[GIT_SHA1_RAWSZ] = {42};
+		reftable_new_writer(&strbuf_add_void, &noop_flush, &buf, &opts);
 	struct reftable_ref_record ref = {
 		.update_index = 1,
 		.value_type = REFTABLE_REF_VAL1,
-		.value.val1 = hash,
+		.value.val1 = {42},
 	};
 	int err;
 	int i;
@@ -709,12 +703,11 @@ static void test_write_object_id_length(void)
 	};
 	struct strbuf buf = STRBUF_INIT;
 	struct reftable_writer *w =
-		reftable_new_writer(&strbuf_add_void, &buf, &opts);
-	uint8_t hash[GIT_SHA1_RAWSZ] = {42};
+		reftable_new_writer(&strbuf_add_void, &noop_flush, &buf, &opts);
 	struct reftable_ref_record ref = {
 		.update_index = 1,
 		.value_type = REFTABLE_REF_VAL1,
-		.value.val1 = hash,
+		.value.val1 = {42},
 	};
 	int err;
 	int i;
@@ -744,7 +737,7 @@ static void test_write_empty_key(void)
 	struct reftable_write_options opts = { 0 };
 	struct strbuf buf = STRBUF_INIT;
 	struct reftable_writer *w =
-		reftable_new_writer(&strbuf_add_void, &buf, &opts);
+		reftable_new_writer(&strbuf_add_void, &noop_flush, &buf, &opts);
 	struct reftable_ref_record ref = {
 		.refname = "",
 		.update_index = 1,
@@ -767,7 +760,7 @@ static void test_write_key_order(void)
 	struct reftable_write_options opts = { 0 };
 	struct strbuf buf = STRBUF_INIT;
 	struct reftable_writer *w =
-		reftable_new_writer(&strbuf_add_void, &buf, &opts);
+		reftable_new_writer(&strbuf_add_void, &noop_flush, &buf, &opts);
 	struct reftable_ref_record refs[2] = {
 		{
 			.refname = "b",
@@ -797,6 +790,139 @@ static void test_write_key_order(void)
 	strbuf_release(&buf);
 }
 
+static void test_write_multiple_indices(void)
+{
+	struct reftable_write_options opts = {
+		.block_size = 100,
+	};
+	struct strbuf writer_buf = STRBUF_INIT, buf = STRBUF_INIT;
+	struct reftable_block_source source = { 0 };
+	struct reftable_iterator it = { 0 };
+	const struct reftable_stats *stats;
+	struct reftable_writer *writer;
+	struct reftable_reader *reader;
+	int err, i;
+
+	writer = reftable_new_writer(&strbuf_add_void, &noop_flush, &writer_buf, &opts);
+	reftable_writer_set_limits(writer, 1, 1);
+	for (i = 0; i < 100; i++) {
+		struct reftable_ref_record ref = {
+			.update_index = 1,
+			.value_type = REFTABLE_REF_VAL1,
+			.value.val1 = {i},
+		};
+
+		strbuf_reset(&buf);
+		strbuf_addf(&buf, "refs/heads/%04d", i);
+		ref.refname = buf.buf,
+
+		err = reftable_writer_add_ref(writer, &ref);
+		EXPECT_ERR(err);
+	}
+
+	for (i = 0; i < 100; i++) {
+		unsigned char hash[GIT_SHA1_RAWSZ] = {i};
+		struct reftable_log_record log = {
+			.update_index = 1,
+			.value_type = REFTABLE_LOG_UPDATE,
+			.value.update = {
+				.old_hash = hash,
+				.new_hash = hash,
+			},
+		};
+
+		strbuf_reset(&buf);
+		strbuf_addf(&buf, "refs/heads/%04d", i);
+		log.refname = buf.buf,
+
+		err = reftable_writer_add_log(writer, &log);
+		EXPECT_ERR(err);
+	}
+
+	reftable_writer_close(writer);
+
+	/*
+	 * The written data should be sufficiently large to result in indices
+	 * for each of the block types.
+	 */
+	stats = reftable_writer_stats(writer);
+	EXPECT(stats->ref_stats.index_offset > 0);
+	EXPECT(stats->obj_stats.index_offset > 0);
+	EXPECT(stats->log_stats.index_offset > 0);
+
+	block_source_from_strbuf(&source, &writer_buf);
+	err = reftable_new_reader(&reader, &source, "filename");
+	EXPECT_ERR(err);
+
+	/*
+	 * Seeking the log uses the log index now. In case there is any
+	 * confusion regarding indices we would notice here.
+	 */
+	err = reftable_reader_seek_log(reader, &it, "");
+	EXPECT_ERR(err);
+
+	reftable_iterator_destroy(&it);
+	reftable_writer_free(writer);
+	reftable_reader_free(reader);
+	strbuf_release(&writer_buf);
+	strbuf_release(&buf);
+}
+
+static void test_write_multi_level_index(void)
+{
+	struct reftable_write_options opts = {
+		.block_size = 100,
+	};
+	struct strbuf writer_buf = STRBUF_INIT, buf = STRBUF_INIT;
+	struct reftable_block_source source = { 0 };
+	struct reftable_iterator it = { 0 };
+	const struct reftable_stats *stats;
+	struct reftable_writer *writer;
+	struct reftable_reader *reader;
+	int err;
+
+	writer = reftable_new_writer(&strbuf_add_void, &noop_flush, &writer_buf, &opts);
+	reftable_writer_set_limits(writer, 1, 1);
+	for (size_t i = 0; i < 200; i++) {
+		struct reftable_ref_record ref = {
+			.update_index = 1,
+			.value_type = REFTABLE_REF_VAL1,
+			.value.val1 = {i},
+		};
+
+		strbuf_reset(&buf);
+		strbuf_addf(&buf, "refs/heads/%03" PRIuMAX, (uintmax_t)i);
+		ref.refname = buf.buf,
+
+		err = reftable_writer_add_ref(writer, &ref);
+		EXPECT_ERR(err);
+	}
+	reftable_writer_close(writer);
+
+	/*
+	 * The written refs should be sufficiently large to result in a
+	 * multi-level index.
+	 */
+	stats = reftable_writer_stats(writer);
+	EXPECT(stats->ref_stats.max_index_level == 2);
+
+	block_source_from_strbuf(&source, &writer_buf);
+	err = reftable_new_reader(&reader, &source, "filename");
+	EXPECT_ERR(err);
+
+	/*
+	 * Seeking the last ref should work as expected.
+	 */
+	err = reftable_reader_seek_ref(reader, &it, "refs/heads/199");
+	EXPECT_ERR(err);
+
+	reftable_iterator_destroy(&it);
+	reftable_writer_free(writer);
+	reftable_reader_free(reader);
+	strbuf_release(&writer_buf);
+	strbuf_release(&buf);
+}
+
 static void test_corrupt_table_empty(void)
 {
 	struct strbuf buf = STRBUF_INIT;
@@ -846,5 +972,7 @@ int readwrite_test_main(int argc, const char *argv[])
 	RUN_TEST(test_log_overflow);
 	RUN_TEST(test_write_object_id_length);
 	RUN_TEST(test_write_object_id_min_length);
+	RUN_TEST(test_write_multiple_indices);
+	RUN_TEST(test_write_multi_level_index);
 	return 0;
 }
diff --git a/reftable/record.c b/reftable/record.c
index fbaa1fb..26c5e43 100644
--- a/reftable/record.c
+++ b/reftable/record.c
@@ -76,7 +76,7 @@ int reftable_is_block_type(uint8_t typ)
 	return 0;
 }
 
-uint8_t *reftable_ref_record_val1(const struct reftable_ref_record *rec)
+const unsigned char *reftable_ref_record_val1(const struct reftable_ref_record *rec)
 {
 	switch (rec->value_type) {
 	case REFTABLE_REF_VAL1:
@@ -88,7 +88,7 @@ uint8_t *reftable_ref_record_val1(const struct reftable_ref_record *rec)
 	}
 }
 
-uint8_t *reftable_ref_record_val2(const struct reftable_ref_record *rec)
+const unsigned char *reftable_ref_record_val2(const struct reftable_ref_record *rec)
 {
 	switch (rec->value_type) {
 	case REFTABLE_REF_VAL2:
@@ -219,13 +219,10 @@ static void reftable_ref_record_copy_from(void *rec, const void *src_rec,
 	case REFTABLE_REF_DELETION:
 		break;
 	case REFTABLE_REF_VAL1:
-		ref->value.val1 = reftable_malloc(hash_size);
 		memcpy(ref->value.val1, src->value.val1, hash_size);
 		break;
 	case REFTABLE_REF_VAL2:
-		ref->value.val2.value = reftable_malloc(hash_size);
 		memcpy(ref->value.val2.value, src->value.val2.value, hash_size);
-		ref->value.val2.target_value = reftable_malloc(hash_size);
 		memcpy(ref->value.val2.target_value,
 		       src->value.val2.target_value, hash_size);
 		break;
@@ -242,7 +239,7 @@ static char hexdigit(int c)
 	return 'a' + (c - 10);
 }
 
-static void hex_format(char *dest, uint8_t *src, int hash_size)
+static void hex_format(char *dest, const unsigned char *src, int hash_size)
 {
 	assert(hash_size > 0);
 	if (src) {
@@ -299,11 +296,8 @@ void reftable_ref_record_release(struct reftable_ref_record *ref)
 		reftable_free(ref->value.symref);
 		break;
 	case REFTABLE_REF_VAL2:
-		reftable_free(ref->value.val2.target_value);
-		reftable_free(ref->value.val2.value);
 		break;
 	case REFTABLE_REF_VAL1:
-		reftable_free(ref->value.val1);
 		break;
 	case REFTABLE_REF_DELETION:
 		break;
@@ -394,7 +388,6 @@ static int reftable_ref_record_decode(void *rec, struct strbuf key,
 			return -1;
 		}
 
-		r->value.val1 = reftable_malloc(hash_size);
 		memcpy(r->value.val1, in.buf, hash_size);
 		string_view_consume(&in, hash_size);
 		break;
@@ -404,11 +397,9 @@ static int reftable_ref_record_decode(void *rec, struct strbuf key,
 			return -1;
 		}
 
-		r->value.val2.value = reftable_malloc(hash_size);
 		memcpy(r->value.val2.value, in.buf, hash_size);
 		string_view_consume(&in, hash_size);
 
-		r->value.val2.target_value = reftable_malloc(hash_size);
 		memcpy(r->value.val2.target_value, in.buf, hash_size);
 		string_view_consume(&in, hash_size);
 		break;
@@ -506,12 +497,13 @@ static void reftable_obj_record_copy_from(void *rec, const void *src_rec,
 		(const struct reftable_obj_record *)src_rec;
 
 	reftable_obj_record_release(obj);
-	obj->hash_prefix = reftable_malloc(src->hash_prefix_len);
+
+	REFTABLE_ALLOC_ARRAY(obj->hash_prefix, src->hash_prefix_len);
 	obj->hash_prefix_len = src->hash_prefix_len;
 	if (src->hash_prefix_len)
 		memcpy(obj->hash_prefix, src->hash_prefix, obj->hash_prefix_len);
 
-	obj->offsets = reftable_malloc(src->offset_len * sizeof(uint64_t));
+	REFTABLE_ALLOC_ARRAY(obj->offsets, src->offset_len);
 	obj->offset_len = src->offset_len;
 	COPY_ARRAY(obj->offsets, src->offsets, src->offset_len);
 }
@@ -568,7 +560,8 @@ static int reftable_obj_record_decode(void *rec, struct strbuf key,
 	int n = 0;
 	uint64_t last;
 	int j;
-	r->hash_prefix = reftable_malloc(key.len);
+
+	REFTABLE_ALLOC_ARRAY(r->hash_prefix, key.len);
 	memcpy(r->hash_prefix, key.buf, key.len);
 	r->hash_prefix_len = key.len;
 
@@ -586,7 +579,7 @@ static int reftable_obj_record_decode(void *rec, struct strbuf key,
 	if (count == 0)
 		return start.len - in.len;
 
-	r->offsets = reftable_malloc(count * sizeof(uint64_t));
+	REFTABLE_ALLOC_ARRAY(r->offsets, count);
 	r->offset_len = count;
 
 	n = get_var_int(&r->offsets[0], &in);
@@ -724,12 +717,12 @@ static void reftable_log_record_copy_from(void *rec, const void *src_rec,
 		}
 
 		if (dst->value.update.new_hash) {
-			dst->value.update.new_hash = reftable_malloc(hash_size);
+			REFTABLE_ALLOC_ARRAY(dst->value.update.new_hash, hash_size);
 			memcpy(dst->value.update.new_hash,
 			       src->value.update.new_hash, hash_size);
 		}
 		if (dst->value.update.old_hash) {
-			dst->value.update.old_hash = reftable_malloc(hash_size);
+			REFTABLE_ALLOC_ARRAY(dst->value.update.old_hash, hash_size);
 			memcpy(dst->value.update.old_hash,
 			       src->value.update.old_hash, hash_size);
 		}
@@ -1164,7 +1157,7 @@ int reftable_record_equal(struct reftable_record *a, struct reftable_record *b,
 		reftable_record_data(a), reftable_record_data(b), hash_size);
 }
 
-static int hash_equal(uint8_t *a, uint8_t *b, int hash_size)
+static int hash_equal(const unsigned char *a, const unsigned char *b, int hash_size)
 {
 	if (a && b)
 		return !memcmp(a, b, hash_size);
@@ -1266,45 +1259,22 @@ reftable_record_vtable(struct reftable_record *rec)
 	abort();
 }
 
-struct reftable_record reftable_new_record(uint8_t typ)
+void reftable_record_init(struct reftable_record *rec, uint8_t typ)
 {
-	struct reftable_record clean = {
-		.type = typ,
-	};
+	memset(rec, 0, sizeof(*rec));
+	rec->type = typ;
 
-	/* the following is involved, but the naive solution (just return
-	 * `clean` as is, except for BLOCK_TYPE_INDEX), returns a garbage
-	 * clean.u.obj.offsets pointer on Windows VS CI.  Go figure.
-	 */
 	switch (typ) {
-	case BLOCK_TYPE_OBJ:
-	{
-		struct reftable_obj_record obj = { 0 };
-		clean.u.obj = obj;
-		break;
-	}
-	case BLOCK_TYPE_INDEX:
-	{
-		struct reftable_index_record idx = {
-			.last_key = STRBUF_INIT,
-		};
-		clean.u.idx = idx;
-		break;
-	}
 	case BLOCK_TYPE_REF:
-	{
-		struct reftable_ref_record ref = { 0 };
-		clean.u.ref = ref;
-		break;
-	}
 	case BLOCK_TYPE_LOG:
-	{
-		struct reftable_log_record log = { 0 };
-		clean.u.log = log;
-		break;
+	case BLOCK_TYPE_OBJ:
+		return;
+	case BLOCK_TYPE_INDEX:
+		strbuf_init(&rec->u.idx.last_key, 0);
+		return;
+	default:
+		BUG("unhandled record type");
 	}
-	}
-	return clean;
 }
 
 void reftable_record_print(struct reftable_record *rec, int hash_size)
diff --git a/reftable/record.h b/reftable/record.h
index fd80cd4..e64ed30 100644
--- a/reftable/record.h
+++ b/reftable/record.h
@@ -69,9 +69,6 @@ struct reftable_record_vtable {
 /* returns true for recognized block types. Block start with the block type. */
 int reftable_is_block_type(uint8_t typ);
 
-/* return an initialized record for the given type */
-struct reftable_record reftable_new_record(uint8_t typ);
-
 /* Encode `key` into `dest`. Sets `is_restart` to indicate a restart. Returns
  * number of bytes written. */
 int reftable_encode_key(int *is_restart, struct string_view dest,
@@ -100,8 +97,8 @@ struct reftable_obj_record {
 /* record is a generic wrapper for different types of records. It is normally
  * created on the stack, or embedded within another struct. If the type is
  * known, a fresh instance can be initialized explicitly. Otherwise, use
- * reftable_new_record() to initialize generically (as the index_record is not
- * valid as 0-initialized structure)
+ * `reftable_record_init()` to initialize generically (as the index_record is
+ * not valid as 0-initialized structure)
  */
 struct reftable_record {
 	uint8_t type;
@@ -113,6 +110,9 @@ struct reftable_record {
 	} u;
 };
 
+/* Initialize the reftable record for the given type */
+void reftable_record_init(struct reftable_record *rec, uint8_t typ);
+
 /* see struct record_vtable */
 int reftable_record_equal(struct reftable_record *a, struct reftable_record *b, int hash_size);
 void reftable_record_print(struct reftable_record *rec, int hash_size);
diff --git a/reftable/record_test.c b/reftable/record_test.c
index 70ae78f..a86cff5 100644
--- a/reftable/record_test.c
+++ b/reftable/record_test.c
@@ -16,11 +16,11 @@
 
 static void test_copy(struct reftable_record *rec)
 {
-	struct reftable_record copy = { 0 };
+	struct reftable_record copy;
 	uint8_t typ;
 
 	typ = reftable_record_type(rec);
-	copy = reftable_new_record(typ);
+	reftable_record_init(&copy, typ);
 	reftable_record_copy_from(&copy, rec, GIT_SHA1_RAWSZ);
 	/* do it twice to catch memory leaks */
 	reftable_record_copy_from(&copy, rec, GIT_SHA1_RAWSZ);
@@ -119,15 +119,10 @@ static void test_reftable_ref_record_roundtrip(void)
 		case REFTABLE_REF_DELETION:
 			break;
 		case REFTABLE_REF_VAL1:
-			in.u.ref.value.val1 = reftable_malloc(GIT_SHA1_RAWSZ);
 			set_hash(in.u.ref.value.val1, 1);
 			break;
 		case REFTABLE_REF_VAL2:
-			in.u.ref.value.val2.value =
-				reftable_malloc(GIT_SHA1_RAWSZ);
 			set_hash(in.u.ref.value.val2.value, 1);
-			in.u.ref.value.val2.target_value =
-				reftable_malloc(GIT_SHA1_RAWSZ);
 			set_hash(in.u.ref.value.val2.target_value, 2);
 			break;
 		case REFTABLE_REF_SYMREF:
@@ -236,8 +231,8 @@ static void test_reftable_log_record_roundtrip(void)
 				.value_type = REFTABLE_LOG_UPDATE,
 				.value = {
 					.update = {
-						.new_hash = reftable_calloc(GIT_SHA1_RAWSZ),
-						.old_hash = reftable_calloc(GIT_SHA1_RAWSZ),
+						.new_hash = reftable_calloc(GIT_SHA1_RAWSZ, 1),
+						.old_hash = reftable_calloc(GIT_SHA1_RAWSZ, 1),
 						.name = xstrdup("old name"),
 						.email = xstrdup("old@email"),
 						.message = xstrdup("old message"),
diff --git a/reftable/refname.c b/reftable/refname.c
index 9573496..7570e4a 100644
--- a/reftable/refname.c
+++ b/reftable/refname.c
@@ -140,8 +140,8 @@ int validate_ref_record_addition(struct reftable_table tab,
 {
 	struct modification mod = {
 		.tab = tab,
-		.add = reftable_calloc(sizeof(char *) * sz),
-		.del = reftable_calloc(sizeof(char *) * sz),
+		.add = reftable_calloc(sz, sizeof(*mod.add)),
+		.del = reftable_calloc(sz, sizeof(*mod.del)),
 	};
 	int i = 0;
 	int err = 0;
diff --git a/reftable/refname_test.c b/reftable/refname_test.c
index 699e1ae..b9cc625 100644
--- a/reftable/refname_test.c
+++ b/reftable/refname_test.c
@@ -30,7 +30,7 @@ static void test_conflict(void)
 	struct reftable_write_options opts = { 0 };
 	struct strbuf buf = STRBUF_INIT;
 	struct reftable_writer *w =
-		reftable_new_writer(&strbuf_add_void, &buf, &opts);
+		reftable_new_writer(&strbuf_add_void, &noop_flush, &buf, &opts);
 	struct reftable_ref_record rec = {
 		.refname = "a/b",
 		.value_type = REFTABLE_REF_SYMREF,
diff --git a/reftable/reftable-merged.h b/reftable/reftable-merged.h
index 1a6d169..c91a2d8 100644
--- a/reftable/reftable-merged.h
+++ b/reftable/reftable-merged.h
@@ -33,7 +33,7 @@ struct reftable_table;
    the stack array.
 */
 int reftable_new_merged_table(struct reftable_merged_table **dest,
-			      struct reftable_table *stack, int n,
+			      struct reftable_table *stack, size_t n,
 			      uint32_t hash_id);
 
 /* returns an iterator positioned just before 'name' */
diff --git a/reftable/reftable-record.h b/reftable/reftable-record.h
index 67104f8..bb6e99a 100644
--- a/reftable/reftable-record.h
+++ b/reftable/reftable-record.h
@@ -9,6 +9,7 @@ license that can be found in the LICENSE file or at
 #ifndef REFTABLE_RECORD_H
 #define REFTABLE_RECORD_H
 
+#include "hash-ll.h"
 #include <stdint.h>
 
 /*
@@ -38,10 +39,10 @@ struct reftable_ref_record {
 #define REFTABLE_NR_REF_VALUETYPES 4
 	} value_type;
 	union {
-		uint8_t *val1; /* malloced hash. */
+		unsigned char val1[GIT_MAX_RAWSZ];
 		struct {
-			uint8_t *value; /* first value, malloced hash  */
-			uint8_t *target_value; /* second value, malloced hash */
+			unsigned char value[GIT_MAX_RAWSZ]; /* first hash  */
+			unsigned char target_value[GIT_MAX_RAWSZ]; /* second hash */
 		} val2;
 		char *symref; /* referent, malloced 0-terminated string */
 	} value;
@@ -49,11 +50,11 @@ struct reftable_ref_record {
 
 /* Returns the first hash, or NULL if `rec` is not of type
  * REFTABLE_REF_VAL1 or REFTABLE_REF_VAL2. */
-uint8_t *reftable_ref_record_val1(const struct reftable_ref_record *rec);
+const unsigned char *reftable_ref_record_val1(const struct reftable_ref_record *rec);
 
 /* Returns the second hash, or NULL if `rec` is not of type
  * REFTABLE_REF_VAL2. */
-uint8_t *reftable_ref_record_val2(const struct reftable_ref_record *rec);
+const unsigned char *reftable_ref_record_val2(const struct reftable_ref_record *rec);
 
 /* returns whether 'ref' represents a deletion */
 int reftable_ref_record_is_deletion(const struct reftable_ref_record *ref);
diff --git a/reftable/reftable-writer.h b/reftable/reftable-writer.h
index db8de19..7c7cae5 100644
--- a/reftable/reftable-writer.h
+++ b/reftable/reftable-writer.h
@@ -88,6 +88,7 @@ struct reftable_stats {
 /* reftable_new_writer creates a new writer */
 struct reftable_writer *
 reftable_new_writer(ssize_t (*writer_func)(void *, const void *, size_t),
+		    int (*flush_func)(void *),
 		    void *writer_arg, struct reftable_write_options *opts);
 
 /* Set the range of update indices for the records we will add. When writing a
diff --git a/reftable/stack.c b/reftable/stack.c
index 16bab82..b64e556 100644
--- a/reftable/stack.c
+++ b/reftable/stack.c
@@ -8,6 +8,7 @@ license that can be found in the LICENSE file or at
 
 #include "stack.h"
 
+#include "../write-or-die.h"
 #include "system.h"
 #include "merged.h"
 #include "reader.h"
@@ -16,7 +17,6 @@ license that can be found in the LICENSE file or at
 #include "reftable-record.h"
 #include "reftable-merged.h"
 #include "writer.h"
-
 #include "tempfile.h"
 
 static int stack_try_add(struct reftable_stack *st,
@@ -24,7 +24,8 @@ static int stack_try_add(struct reftable_stack *st,
 					    void *arg),
 			 void *arg);
 static int stack_write_compact(struct reftable_stack *st,
-			       struct reftable_writer *wr, int first, int last,
+			       struct reftable_writer *wr,
+			       size_t first, size_t last,
 			       struct reftable_log_expiry_config *config);
 static int stack_check_addition(struct reftable_stack *st,
 				const char *new_tab_name);
@@ -47,11 +48,17 @@ static ssize_t reftable_fd_write(void *arg, const void *data, size_t sz)
 	return write_in_full(*fdp, data, sz);
 }
 
+static int reftable_fd_flush(void *arg)
+{
+	int *fdp = (int *)arg;
+
+	return fsync_component(FSYNC_COMPONENT_REFERENCE, *fdp);
+}
+
 int reftable_new_stack(struct reftable_stack **dest, const char *dir,
 		       struct reftable_write_options config)
 {
-	struct reftable_stack *p =
-		reftable_calloc(sizeof(struct reftable_stack));
+	struct reftable_stack *p = reftable_calloc(1, sizeof(*p));
 	struct strbuf list_file_name = STRBUF_INIT;
 	int err = 0;
 
@@ -66,6 +73,7 @@ int reftable_new_stack(struct reftable_stack **dest, const char *dir,
 	strbuf_addstr(&list_file_name, "/tables.list");
 
 	p->list_file = strbuf_detach(&list_file_name, NULL);
+	p->list_fd = -1;
 	p->reftable_dir = xstrdup(dir);
 	p->config = config;
 
@@ -93,7 +101,7 @@ static int fd_read_lines(int fd, char ***namesp)
 		goto done;
 	}
 
-	buf = reftable_malloc(size + 1);
+	REFTABLE_ALLOC_ARRAY(buf, size + 1);
 	if (read_in_full(fd, buf, size) != size) {
 		err = REFTABLE_IO_ERROR;
 		goto done;
@@ -113,7 +121,7 @@ int read_lines(const char *filename, char ***namesp)
 	int err = 0;
 	if (fd < 0) {
 		if (errno == ENOENT) {
-			*namesp = reftable_calloc(sizeof(char *));
+			REFTABLE_CALLOC_ARRAY(*namesp, 1);
 			return 0;
 		}
 
@@ -175,6 +183,12 @@ void reftable_stack_destroy(struct reftable_stack *st)
 		st->readers_len = 0;
 		FREE_AND_NULL(st->readers);
 	}
+
+	if (st->list_fd >= 0) {
+		close(st->list_fd);
+		st->list_fd = -1;
+	}
+
 	FREE_AND_NULL(st->list_file);
 	FREE_AND_NULL(st->reftable_dir);
 	reftable_free(st);
@@ -184,8 +198,7 @@ void reftable_stack_destroy(struct reftable_stack *st)
 static struct reftable_reader **stack_copy_readers(struct reftable_stack *st,
 						   int cur_len)
 {
-	struct reftable_reader **cur =
-		reftable_calloc(sizeof(struct reftable_reader *) * cur_len);
+	struct reftable_reader **cur = reftable_calloc(cur_len, sizeof(*cur));
 	int i = 0;
 	for (i = 0; i < cur_len; i++) {
 		cur[i] = st->readers[i];
@@ -196,18 +209,18 @@ static struct reftable_reader **stack_copy_readers(struct reftable_stack *st,
 static int reftable_stack_reload_once(struct reftable_stack *st, char **names,
 				      int reuse_open)
 {
-	int cur_len = !st->merged ? 0 : st->merged->stack_len;
+	size_t cur_len = !st->merged ? 0 : st->merged->stack_len;
 	struct reftable_reader **cur = stack_copy_readers(st, cur_len);
-	int err = 0;
-	int names_len = names_length(names);
+	size_t names_len = names_length(names);
 	struct reftable_reader **new_readers =
-		reftable_calloc(sizeof(struct reftable_reader *) * names_len);
+		reftable_calloc(names_len, sizeof(*new_readers));
 	struct reftable_table *new_tables =
-		reftable_calloc(sizeof(struct reftable_table) * names_len);
-	int new_readers_len = 0;
+		reftable_calloc(names_len, sizeof(*new_tables));
+	size_t new_readers_len = 0;
 	struct reftable_merged_table *new_merged = NULL;
 	struct strbuf table_path = STRBUF_INIT;
-	int i;
+	int err = 0;
+	size_t i;
 
 	while (*names) {
 		struct reftable_reader *rd = NULL;
@@ -215,11 +228,10 @@ static int reftable_stack_reload_once(struct reftable_stack *st, char **names,
 
 		/* this is linear; we assume compaction keeps the number of
 		   tables under control so this is not quadratic. */
-		int j = 0;
-		for (j = 0; reuse_open && j < cur_len; j++) {
-			if (cur[j] && 0 == strcmp(cur[j]->name, name)) {
-				rd = cur[j];
-				cur[j] = NULL;
+		for (i = 0; reuse_open && i < cur_len; i++) {
+			if (cur[i] && 0 == strcmp(cur[i]->name, name)) {
+				rd = cur[i];
+				cur[i] = NULL;
 				break;
 			}
 		}
@@ -304,69 +316,134 @@ static int tv_cmp(struct timeval *a, struct timeval *b)
 static int reftable_stack_reload_maybe_reuse(struct reftable_stack *st,
 					     int reuse_open)
 {
-	struct timeval deadline = { 0 };
-	int err = gettimeofday(&deadline, NULL);
+	char **names = NULL, **names_after = NULL;
+	struct timeval deadline;
 	int64_t delay = 0;
-	int tries = 0;
+	int tries = 0, err;
+	int fd = -1;
+
+	err = gettimeofday(&deadline, NULL);
 	if (err < 0)
-		return err;
-
+		goto out;
 	deadline.tv_sec += 3;
+
 	while (1) {
-		char **names = NULL;
-		char **names_after = NULL;
-		struct timeval now = { 0 };
-		int err = gettimeofday(&now, NULL);
-		int err2 = 0;
-		if (err < 0) {
-			return err;
-		}
+		struct timeval now;
 
-		/* Only look at deadlines after the first few times. This
-		   simplifies debugging in GDB */
+		err = gettimeofday(&now, NULL);
+		if (err < 0)
+			goto out;
+
+		/*
+		 * Only look at deadlines after the first few times. This
+		 * simplifies debugging in GDB.
+		 */
 		tries++;
-		if (tries > 3 && tv_cmp(&now, &deadline) >= 0) {
-			break;
+		if (tries > 3 && tv_cmp(&now, &deadline) >= 0)
+			goto out;
+
+		fd = open(st->list_file, O_RDONLY);
+		if (fd < 0) {
+			if (errno != ENOENT) {
+				err = REFTABLE_IO_ERROR;
+				goto out;
+			}
+
+			REFTABLE_CALLOC_ARRAY(names, 1);
+		} else {
+			err = fd_read_lines(fd, &names);
+			if (err < 0)
+				goto out;
 		}
 
-		err = read_lines(st->list_file, &names);
-		if (err < 0) {
-			free_names(names);
-			return err;
-		}
 		err = reftable_stack_reload_once(st, names, reuse_open);
-		if (err == 0) {
-			free_names(names);
+		if (!err)
 			break;
-		}
-		if (err != REFTABLE_NOT_EXIST_ERROR) {
-			free_names(names);
-			return err;
-		}
+		if (err != REFTABLE_NOT_EXIST_ERROR)
+			goto out;
 
-		/* err == REFTABLE_NOT_EXIST_ERROR can be caused by a concurrent
-		   writer. Check if there was one by checking if the name list
-		   changed.
-		*/
-		err2 = read_lines(st->list_file, &names_after);
-		if (err2 < 0) {
-			free_names(names);
-			return err2;
-		}
-
+		/*
+		 * REFTABLE_NOT_EXIST_ERROR can be caused by a concurrent
+		 * writer. Check if there was one by checking if the name list
+		 * changed.
+		 */
+		err = read_lines(st->list_file, &names_after);
+		if (err < 0)
+			goto out;
 		if (names_equal(names_after, names)) {
-			free_names(names);
-			free_names(names_after);
-			return err;
+			err = REFTABLE_NOT_EXIST_ERROR;
+			goto out;
 		}
+
 		free_names(names);
+		names = NULL;
 		free_names(names_after);
+		names_after = NULL;
+		close(fd);
+		fd = -1;
 
 		delay = delay + (delay * rand()) / RAND_MAX + 1;
 		sleep_millisec(delay);
 	}
 
-	return 0;
+out:
+	/*
+	 * Invalidate the stat cache. It is sufficient to only close the file
+	 * descriptor and keep the cached stat info because we never use the
+	 * latter when the former is negative.
+	 */
+	if (st->list_fd >= 0) {
+		close(st->list_fd);
+		st->list_fd = -1;
+	}
+
+	/*
+	 * Cache stat information in case it provides a useful signal to us.
+	 * According to POSIX, "The st_ino and st_dev fields taken together
+	 * uniquely identify the file within the system." That being said,
+	 * Windows is not POSIX compliant and we do not have these fields
+	 * available. So the information we have there is insufficient to
+	 * determine whether two file descriptors point to the same file.
+	 *
+	 * While we could fall back to using other signals like the file's
+	 * mtime, those are not sufficient to avoid races. We thus refrain from
+	 * using the stat cache on such systems and fall back to the secondary
+	 * caching mechanism, which is to check whether contents of the file
+	 * have changed.
+	 *
+	 * On other systems which are POSIX compliant we must keep the file
+	 * descriptor open. This is to avoid a race condition where two
+	 * processes access the reftable stack at the same point in time:
+	 *
+	 *   1. A reads the reftable stack and caches its stat info.
+	 *
+	 *   2. B updates the stack, appending a new table to "tables.list".
+	 *      This will both use a new inode and result in a different file
+	 *      size, thus invalidating A's cache in theory.
+	 *
+	 *   3. B decides to auto-compact the stack and merges two tables. The
+	 *      file size now matches what A has cached again. Furthermore, the
+	 *      filesystem may decide to recycle the inode number of the file
+	 *      we have replaced in (2) because it is not in use anymore.
+	 *
+	 *   4. A reloads the reftable stack. Neither the inode number nor the
+	 *      file size changed. If the timestamps did not change either then
+	 *      we think the cached copy of our stack is up-to-date.
+	 *
+	 * By keeping the file descriptor open the inode number cannot be
+	 * recycled, mitigating the race.
+	 */
+	if (!err && fd >= 0 && !fstat(fd, &st->list_st) &&
+	    st->list_st.st_dev && st->list_st.st_ino) {
+		st->list_fd = fd;
+		fd = -1;
+	}
+
+	if (fd >= 0)
+		close(fd);
+	free_names(names);
+	free_names(names_after);
+	return err;
 }
 
 /* -1 = error
@@ -375,8 +452,44 @@ static int reftable_stack_reload_maybe_reuse(struct reftable_stack *st,
 static int stack_uptodate(struct reftable_stack *st)
 {
 	char **names = NULL;
-	int err = read_lines(st->list_file, &names);
+	int err;
 	int i = 0;
+
+	/*
+	 * When we have cached stat information available then we use it to
+	 * verify whether the file has been rewritten.
+	 *
+	 * Note that we explicitly do not want to use `stat_validity_check()`
+	 * and friends here because they may end up not comparing the `st_dev`
+	 * and `st_ino` fields. These functions thus cannot guarantee that we
+	 * indeed still have the same file.
+	 */
+	if (st->list_fd >= 0) {
+		struct stat list_st;
+
+		if (stat(st->list_file, &list_st) < 0) {
+			/*
+			 * It's fine for "tables.list" to not exist. In that
+			 * case, we have to refresh when the loaded stack has
+			 * any readers.
+			 */
+			if (errno == ENOENT)
+				return !!st->readers_len;
+			return REFTABLE_IO_ERROR;
+		}
+
+		/*
+		 * When "tables.list" refers to the same file we can assume
+		 * that it didn't change. This is because we always use
+		 * rename(3P) to update the file and never write to it
+		 * directly.
+		 */
+		if (st->list_st.st_dev == list_st.st_dev &&
+		    st->list_st.st_ino == list_st.st_ino)
+			return 0;
+	}
+
+	err = read_lines(st->list_file, &names);
 	if (err < 0)
 		return err;
 
@@ -425,9 +538,6 @@ int reftable_stack_add(struct reftable_stack *st,
 		return err;
 	}
 
-	if (!st->disable_auto_compact)
-		return reftable_stack_auto_compact(st);
-
 	return 0;
 }
 
@@ -446,7 +556,7 @@ struct reftable_addition {
 	struct reftable_stack *stack;
 
 	char **new_tables;
-	int new_tables_len;
+	size_t new_tables_len, new_tables_cap;
 	uint64_t next_update_index;
 };
 
@@ -497,8 +607,9 @@ static int reftable_stack_init_addition(struct reftable_addition *add,
 
 static void reftable_addition_close(struct reftable_addition *add)
 {
-	int i = 0;
 	struct strbuf nm = STRBUF_INIT;
+	size_t i;
+
 	for (i = 0; i < add->new_tables_len; i++) {
 		stack_filename(&nm, add->stack, add->new_tables[i]);
 		unlink(nm.buf);
@@ -508,6 +619,7 @@ static void reftable_addition_close(struct reftable_addition *add)
 	reftable_free(add->new_tables);
 	add->new_tables = NULL;
 	add->new_tables_len = 0;
+	add->new_tables_cap = 0;
 
 	delete_tempfile(&add->lock_file);
 	strbuf_release(&nm);
@@ -526,8 +638,8 @@ int reftable_addition_commit(struct reftable_addition *add)
 {
 	struct strbuf table_list = STRBUF_INIT;
 	int lock_file_fd = get_tempfile_fd(add->lock_file);
-	int i = 0;
 	int err = 0;
+	size_t i;
 
 	if (add->new_tables_len == 0)
 		goto done;
@@ -548,6 +660,9 @@ int reftable_addition_commit(struct reftable_addition *add)
 		goto done;
 	}
 
+	fsync_component_or_die(FSYNC_COMPONENT_REFERENCE, lock_file_fd,
+			       get_tempfile_path(add->lock_file));
+
 	err = rename_tempfile(&add->lock_file, add->stack->list_file);
 	if (err < 0) {
 		err = REFTABLE_IO_ERROR;
@@ -555,14 +670,14 @@ int reftable_addition_commit(struct reftable_addition *add)
 	}
 
 	/* success, no more state to clean up. */
-	for (i = 0; i < add->new_tables_len; i++) {
+	for (i = 0; i < add->new_tables_len; i++)
 		reftable_free(add->new_tables[i]);
-	}
 	reftable_free(add->new_tables);
 	add->new_tables = NULL;
 	add->new_tables_len = 0;
+	add->new_tables_cap = 0;
 
-	err = reftable_stack_reload(add->stack);
+	err = reftable_stack_reload_maybe_reuse(add->stack, 1);
 	if (err)
 		goto done;
 
@@ -579,7 +694,7 @@ int reftable_stack_new_addition(struct reftable_addition **dest,
 {
 	int err = 0;
 	struct reftable_addition empty = REFTABLE_ADDITION_INIT;
-	*dest = reftable_calloc(sizeof(**dest));
+	REFTABLE_CALLOC_ARRAY(*dest, 1);
 	**dest = empty;
 	err = reftable_stack_init_addition(*dest, st);
 	if (err) {
@@ -642,7 +757,7 @@ int reftable_addition_add(struct reftable_addition *add,
 			goto done;
 		}
 	}
-	wr = reftable_new_writer(reftable_fd_write, &tab_fd,
+	wr = reftable_new_writer(reftable_fd_write, reftable_fd_flush, &tab_fd,
 				 &add->stack->config);
 	err = write_table(wr, arg);
 	if (err < 0)
@@ -687,11 +802,9 @@ int reftable_addition_add(struct reftable_addition *add,
 		goto done;
 	}
 
-	add->new_tables = reftable_realloc(add->new_tables,
-					   sizeof(*add->new_tables) *
-						   (add->new_tables_len + 1));
-	add->new_tables[add->new_tables_len] = strbuf_detach(&next_name, NULL);
-	add->new_tables_len++;
+	REFTABLE_ALLOC_GROW(add->new_tables, add->new_tables_len + 1,
+			    add->new_tables_cap);
+	add->new_tables[add->new_tables_len++] = strbuf_detach(&next_name, NULL);
 done:
 	if (tab_fd > 0) {
 		close(tab_fd);
@@ -717,7 +830,8 @@ uint64_t reftable_stack_next_update_index(struct reftable_stack *st)
 	return 1;
 }
 
-static int stack_compact_locked(struct reftable_stack *st, int first, int last,
+static int stack_compact_locked(struct reftable_stack *st,
+				size_t first, size_t last,
 				struct strbuf *temp_tab,
 				struct reftable_log_expiry_config *config)
 {
@@ -734,7 +848,13 @@ static int stack_compact_locked(struct reftable_stack *st, int first, int last,
 	strbuf_addstr(temp_tab, ".temp.XXXXXX");
 
 	tab_fd = mkstemp(temp_tab->buf);
-	wr = reftable_new_writer(reftable_fd_write, &tab_fd, &st->config);
+	if (st->config.default_permissions &&
+	    chmod(temp_tab->buf, st->config.default_permissions) < 0) {
+		err = REFTABLE_IO_ERROR;
+		goto done;
+	}
+
+	wr = reftable_new_writer(reftable_fd_write, reftable_fd_flush, &tab_fd, &st->config);
 
 	err = stack_write_compact(st, wr, first, last, config);
 	if (err < 0)
@@ -761,22 +881,21 @@ static int stack_compact_locked(struct reftable_stack *st, int first, int last,
 }
 
 static int stack_write_compact(struct reftable_stack *st,
-			       struct reftable_writer *wr, int first, int last,
+			       struct reftable_writer *wr,
+			       size_t first, size_t last,
 			       struct reftable_log_expiry_config *config)
 {
-	int subtabs_len = last - first + 1;
+	size_t subtabs_len = last - first + 1;
 	struct reftable_table *subtabs = reftable_calloc(
-		sizeof(struct reftable_table) * (last - first + 1));
+		last - first + 1, sizeof(*subtabs));
 	struct reftable_merged_table *mt = NULL;
-	int err = 0;
 	struct reftable_iterator it = { NULL };
 	struct reftable_ref_record ref = { NULL };
 	struct reftable_log_record log = { NULL };
-
 	uint64_t entries = 0;
+	int err = 0;
 
-	int i = 0, j = 0;
-	for (i = first, j = 0; i <= last; i++) {
+	for (size_t i = first, j = 0; i <= last; i++) {
 		struct reftable_reader *t = st->readers[i];
 		reftable_table_from_reader(&subtabs[j++], t);
 		st->stats.bytes += t->size;
@@ -801,18 +920,16 @@ static int stack_write_compact(struct reftable_stack *st,
 			err = 0;
 			break;
 		}
-		if (err < 0) {
-			break;
-		}
+		if (err < 0)
+			goto done;
 
 		if (first == 0 && reftable_ref_record_is_deletion(&ref)) {
 			continue;
 		}
 
 		err = reftable_writer_add_ref(wr, &ref);
-		if (err < 0) {
-			break;
-		}
+		if (err < 0)
+			goto done;
 		entries++;
 	}
 	reftable_iterator_destroy(&it);
@@ -827,9 +944,8 @@ static int stack_write_compact(struct reftable_stack *st,
 			err = 0;
 			break;
 		}
-		if (err < 0) {
-			break;
-		}
+		if (err < 0)
+			goto done;
 		if (first == 0 && reftable_log_record_is_deletion(&log)) {
 			continue;
 		}
@@ -845,9 +961,8 @@ static int stack_write_compact(struct reftable_stack *st,
 		}
 
 		err = reftable_writer_add_log(wr, &log);
-		if (err < 0) {
-			break;
-		}
+		if (err < 0)
+			goto done;
 		entries++;
 	}
 
@@ -864,25 +979,20 @@ static int stack_write_compact(struct reftable_stack *st,
 }
 
 /* <  0: error. 0 == OK, > 0 attempt failed; could retry. */
-static int stack_compact_range(struct reftable_stack *st, int first, int last,
+static int stack_compact_range(struct reftable_stack *st,
+			       size_t first, size_t last,
 			       struct reftable_log_expiry_config *expiry)
 {
+	char **delete_on_success = NULL, **subtable_locks = NULL, **listp = NULL;
 	struct strbuf temp_tab_file_name = STRBUF_INIT;
 	struct strbuf new_table_name = STRBUF_INIT;
 	struct strbuf lock_file_name = STRBUF_INIT;
 	struct strbuf ref_list_contents = STRBUF_INIT;
 	struct strbuf new_table_path = STRBUF_INIT;
+	size_t i, j, compact_count;
 	int err = 0;
 	int have_lock = 0;
 	int lock_file_fd = -1;
-	int compact_count = last - first + 1;
-	char **listp = NULL;
-	char **delete_on_success =
-		reftable_calloc(sizeof(char *) * (compact_count + 1));
-	char **subtable_locks =
-		reftable_calloc(sizeof(char *) * (compact_count + 1));
-	int i = 0;
-	int j = 0;
 	int is_empty_table = 0;
 
 	if (first > last || (!expiry && first == last)) {
@@ -890,6 +1000,10 @@ static int stack_compact_range(struct reftable_stack *st, int first, int last,
 		goto done;
 	}
 
+	compact_count = last - first + 1;
+	REFTABLE_CALLOC_ARRAY(delete_on_success, compact_count + 1);
+	REFTABLE_CALLOC_ARRAY(subtable_locks, compact_count + 1);
+
 	st->stats.attempts++;
 
 	strbuf_reset(&lock_file_name);
@@ -1015,6 +1129,14 @@ static int stack_compact_range(struct reftable_stack *st, int first, int last,
 		unlink(new_table_path.buf);
 		goto done;
 	}
+
+	err = fsync_component(FSYNC_COMPONENT_REFERENCE, lock_file_fd);
+	if (err < 0) {
+		err = REFTABLE_IO_ERROR;
+		unlink(new_table_path.buf);
+		goto done;
+	}
+
 	err = close(lock_file_fd);
 	lock_file_fd = -1;
 	if (err < 0) {
@@ -1047,12 +1169,14 @@ static int stack_compact_range(struct reftable_stack *st, int first, int last,
 done:
 	free_names(delete_on_success);
 
-	listp = subtable_locks;
-	while (*listp) {
-		unlink(*listp);
-		listp++;
+	if (subtable_locks) {
+		listp = subtable_locks;
+		while (*listp) {
+			unlink(*listp);
+			listp++;
+		}
+		free_names(subtable_locks);
 	}
-	free_names(subtable_locks);
 	if (lock_file_fd >= 0) {
 		close(lock_file_fd);
 		lock_file_fd = -1;
@@ -1071,17 +1195,17 @@ static int stack_compact_range(struct reftable_stack *st, int first, int last,
 int reftable_stack_compact_all(struct reftable_stack *st,
 			       struct reftable_log_expiry_config *config)
 {
-	return stack_compact_range(st, 0, st->merged->stack_len - 1, config);
+	return stack_compact_range(st, 0, st->merged->stack_len ?
+			st->merged->stack_len - 1 : 0, config);
 }
 
-static int stack_compact_range_stats(struct reftable_stack *st, int first,
-				     int last,
+static int stack_compact_range_stats(struct reftable_stack *st,
+				     size_t first, size_t last,
 				     struct reftable_log_expiry_config *config)
 {
 	int err = stack_compact_range(st, first, last, config);
-	if (err > 0) {
+	if (err > 0)
 		st->stats.failures++;
-	}
 	return err;
 }
 
@@ -1101,12 +1225,11 @@ int fastlog2(uint64_t sz)
 	return l - 1;
 }
 
-struct segment *sizes_to_segments(int *seglen, uint64_t *sizes, int n)
+struct segment *sizes_to_segments(size_t *seglen, uint64_t *sizes, size_t n)
 {
-	struct segment *segs = reftable_calloc(sizeof(struct segment) * n);
-	int next = 0;
+	struct segment *segs = reftable_calloc(n, sizeof(*segs));
 	struct segment cur = { 0 };
-	int i = 0;
+	size_t next = 0, i;
 
 	if (n == 0) {
 		*seglen = 0;
@@ -1132,29 +1255,27 @@ struct segment *sizes_to_segments(int *seglen, uint64_t *sizes, int n)
 	return segs;
 }
 
-struct segment suggest_compaction_segment(uint64_t *sizes, int n)
+struct segment suggest_compaction_segment(uint64_t *sizes, size_t n)
 {
-	int seglen = 0;
-	struct segment *segs = sizes_to_segments(&seglen, sizes, n);
 	struct segment min_seg = {
 		.log = 64,
 	};
-	int i = 0;
-	for (i = 0; i < seglen; i++) {
-		if (segment_size(&segs[i]) == 1) {
-			continue;
-		}
+	struct segment *segs;
+	size_t seglen = 0, i;
 
-		if (segs[i].log < min_seg.log) {
+	segs = sizes_to_segments(&seglen, sizes, n);
+	for (i = 0; i < seglen; i++) {
+		if (segment_size(&segs[i]) == 1)
+			continue;
+
+		if (segs[i].log < min_seg.log)
 			min_seg = segs[i];
-		}
 	}
 
 	while (min_seg.start > 0) {
-		int prev = min_seg.start - 1;
-		if (fastlog2(min_seg.bytes) < fastlog2(sizes[prev])) {
+		size_t prev = min_seg.start - 1;
+		if (fastlog2(min_seg.bytes) < fastlog2(sizes[prev]))
 			break;
-		}
 
 		min_seg.start = prev;
 		min_seg.bytes += sizes[prev];
@@ -1167,7 +1288,7 @@ struct segment suggest_compaction_segment(uint64_t *sizes, int n)
 static uint64_t *stack_table_sizes_for_compaction(struct reftable_stack *st)
 {
 	uint64_t *sizes =
-		reftable_calloc(sizeof(uint64_t) * st->merged->stack_len);
+		reftable_calloc(st->merged->stack_len, sizeof(*sizes));
 	int version = (st->config.hash_id == GIT_SHA1_FORMAT_ID) ? 1 : 2;
 	int overhead = header_size(version) - 1;
 	int i = 0;
@@ -1266,17 +1387,12 @@ static int stack_check_addition(struct reftable_stack *st,
 	while (1) {
 		struct reftable_ref_record ref = { NULL };
 		err = reftable_iterator_next_ref(&it, &ref);
-		if (err > 0) {
+		if (err > 0)
 			break;
-		}
 		if (err < 0)
 			goto done;
 
-		if (len >= cap) {
-			cap = 2 * cap + 1;
-			refs = reftable_realloc(refs, cap * sizeof(refs[0]));
-		}
-
+		REFTABLE_ALLOC_GROW(refs, len + 1, cap);
 		refs[len++] = ref;
 	}
 
diff --git a/reftable/stack.h b/reftable/stack.h
index f570058..d919455 100644
--- a/reftable/stack.h
+++ b/reftable/stack.h
@@ -14,7 +14,10 @@ license that can be found in the LICENSE file or at
 #include "reftable-stack.h"
 
 struct reftable_stack {
+	struct stat list_st;
 	char *list_file;
+	int list_fd;
+
 	char *reftable_dir;
 	int disable_auto_compact;
 
@@ -29,13 +32,13 @@ struct reftable_stack {
 int read_lines(const char *filename, char ***lines);
 
 struct segment {
-	int start, end;
+	size_t start, end;
 	int log;
 	uint64_t bytes;
 };
 
 int fastlog2(uint64_t sz);
-struct segment *sizes_to_segments(int *seglen, uint64_t *sizes, int n);
-struct segment suggest_compaction_segment(uint64_t *sizes, int n);
+struct segment *sizes_to_segments(size_t *seglen, uint64_t *sizes, size_t n);
+struct segment suggest_compaction_segment(uint64_t *sizes, size_t n);
 
 #endif
diff --git a/reftable/stack_test.c b/reftable/stack_test.c
index 82280c2..509f486 100644
--- a/reftable/stack_test.c
+++ b/reftable/stack_test.c
@@ -443,15 +443,16 @@ static void test_reftable_stack_add(void)
 	int err = 0;
 	struct reftable_write_options cfg = {
 		.exact_log_message = 1,
+		.default_permissions = 0660,
 	};
 	struct reftable_stack *st = NULL;
 	char *dir = get_tmp_dir(__LINE__);
-
 	struct reftable_ref_record refs[2] = { { NULL } };
 	struct reftable_log_record logs[2] = { { NULL } };
+	struct strbuf path = STRBUF_INIT;
+	struct stat stat_result;
 	int N = ARRAY_SIZE(refs);
 
-
 	err = reftable_new_stack(&st, dir, cfg);
 	EXPECT_ERR(err);
 	st->disable_auto_compact = 1;
@@ -462,7 +463,6 @@ static void test_reftable_stack_add(void)
 		refs[i].refname = xstrdup(buf);
 		refs[i].update_index = i + 1;
 		refs[i].value_type = REFTABLE_REF_VAL1;
-		refs[i].value.val1 = reftable_malloc(GIT_SHA1_RAWSZ);
 		set_test_hash(refs[i].value.val1, i);
 
 		logs[i].refname = xstrdup(buf);
@@ -510,12 +510,32 @@ static void test_reftable_stack_add(void)
 		reftable_log_record_release(&dest);
 	}
 
+#ifndef GIT_WINDOWS_NATIVE
+	strbuf_addstr(&path, dir);
+	strbuf_addstr(&path, "/tables.list");
+	err = stat(path.buf, &stat_result);
+	EXPECT(!err);
+	EXPECT((stat_result.st_mode & 0777) == cfg.default_permissions);
+
+	strbuf_reset(&path);
+	strbuf_addstr(&path, dir);
+	strbuf_addstr(&path, "/");
+	/* do not try at home; not an external API for reftable. */
+	strbuf_addstr(&path, st->readers[0]->name);
+	err = stat(path.buf, &stat_result);
+	EXPECT(!err);
+	EXPECT((stat_result.st_mode & 0777) == cfg.default_permissions);
+#else
+	(void) stat_result;
+#endif
+
 	/* cleanup */
 	reftable_stack_destroy(st);
 	for (i = 0; i < N; i++) {
 		reftable_ref_record_release(&refs[i]);
 		reftable_log_record_release(&logs[i]);
 	}
+	strbuf_release(&path);
 	clear_dir(dir);
 }
 
@@ -599,7 +619,6 @@ static void test_reftable_stack_tombstone(void)
 		refs[i].update_index = i + 1;
 		if (i % 2 == 0) {
 			refs[i].value_type = REFTABLE_REF_VAL1;
-			refs[i].value.val1 = reftable_malloc(GIT_SHA1_RAWSZ);
 			set_test_hash(refs[i].value.val1, i);
 		}
 
@@ -713,7 +732,7 @@ static void test_sizes_to_segments(void)
 	uint64_t sizes[] = { 2, 3, 4, 5, 7, 9 };
 	/* .................0  1  2  3  4  5 */
 
-	int seglen = 0;
+	size_t seglen = 0;
 	struct segment *segs =
 		sizes_to_segments(&seglen, sizes, ARRAY_SIZE(sizes));
 	EXPECT(segs[2].log == 3);
@@ -728,7 +747,7 @@ static void test_sizes_to_segments(void)
 
 static void test_sizes_to_segments_empty(void)
 {
-	int seglen = 0;
+	size_t seglen = 0;
 	struct segment *segs = sizes_to_segments(&seglen, NULL, 0);
 	EXPECT(seglen == 0);
 	reftable_free(segs);
@@ -737,8 +756,7 @@ static void test_sizes_to_segments_empty(void)
 static void test_sizes_to_segments_all_equal(void)
 {
 	uint64_t sizes[] = { 5, 5 };
-
-	int seglen = 0;
+	size_t seglen = 0;
 	struct segment *segs =
 		sizes_to_segments(&seglen, sizes, ARRAY_SIZE(sizes));
 	EXPECT(seglen == 1);
diff --git a/reftable/test_framework.c b/reftable/test_framework.c
index 04044fc..4066924 100644
--- a/reftable/test_framework.c
+++ b/reftable/test_framework.c
@@ -20,3 +20,8 @@ ssize_t strbuf_add_void(void *b, const void *data, size_t sz)
 	strbuf_add(b, data, sz);
 	return sz;
 }
+
+int noop_flush(void *arg)
+{
+	return 0;
+}
diff --git a/reftable/test_framework.h b/reftable/test_framework.h
index ee44f73..687390f 100644
--- a/reftable/test_framework.h
+++ b/reftable/test_framework.h
@@ -56,4 +56,6 @@ void set_test_hash(uint8_t *p, int i);
  */
 ssize_t strbuf_add_void(void *b, const void *data, size_t sz);
 
+int noop_flush(void *);
+
 #endif
diff --git a/reftable/tree.c b/reftable/tree.c
index a5bf880..528f33a 100644
--- a/reftable/tree.c
+++ b/reftable/tree.c
@@ -20,8 +20,8 @@ struct tree_node *tree_search(void *key, struct tree_node **rootp,
 		if (!insert) {
 			return NULL;
 		} else {
-			struct tree_node *n =
-				reftable_calloc(sizeof(struct tree_node));
+			struct tree_node *n;
+			REFTABLE_CALLOC_ARRAY(n, 1);
 			n->key = key;
 			*rootp = n;
 			return *rootp;
diff --git a/reftable/writer.c b/reftable/writer.c
index 2e322a5..1d9ff0f 100644
--- a/reftable/writer.c
+++ b/reftable/writer.c
@@ -49,7 +49,7 @@ static int padded_write(struct reftable_writer *w, uint8_t *data, size_t len,
 {
 	int n = 0;
 	if (w->pending_padding > 0) {
-		uint8_t *zeroed = reftable_calloc(w->pending_padding);
+		uint8_t *zeroed = reftable_calloc(w->pending_padding, sizeof(*zeroed));
 		int n = w->write(w->write_arg, zeroed, w->pending_padding);
 		if (n < 0)
 			return n;
@@ -121,10 +121,10 @@ static struct strbuf reftable_empty_strbuf = STRBUF_INIT;
 
 struct reftable_writer *
 reftable_new_writer(ssize_t (*writer_func)(void *, const void *, size_t),
+		    int (*flush_func)(void *),
 		    void *writer_arg, struct reftable_write_options *opts)
 {
-	struct reftable_writer *wp =
-		reftable_calloc(sizeof(struct reftable_writer));
+	struct reftable_writer *wp = reftable_calloc(1, sizeof(*wp));
 	strbuf_init(&wp->block_writer_data.last_key, 0);
 	options_set_defaults(opts);
 	if (opts->block_size >= (1 << 24)) {
@@ -132,10 +132,11 @@ reftable_new_writer(ssize_t (*writer_func)(void *, const void *, size_t),
 		abort();
 	}
 	wp->last_key = reftable_empty_strbuf;
-	wp->block = reftable_calloc(opts->block_size);
+	REFTABLE_CALLOC_ARRAY(wp->block, opts->block_size);
 	wp->write = writer_func;
 	wp->write_arg = writer_arg;
 	wp->opts = *opts;
+	wp->flush = flush_func;
 	writer_reinit_block_writer(wp, BLOCK_TYPE_REF);
 
 	return wp;
@@ -200,12 +201,7 @@ static void writer_index_hash(struct reftable_writer *w, struct strbuf *hash)
 		return;
 	}
 
-	if (key->offset_len == key->offset_cap) {
-		key->offset_cap = 2 * key->offset_cap + 1;
-		key->offsets = reftable_realloc(
-			key->offsets, sizeof(uint64_t) * key->offset_cap);
-	}
-
+	REFTABLE_ALLOC_GROW(key->offsets, key->offset_len + 1, key->offset_cap);
 	key->offsets[key->offset_len++] = off;
 }
 
@@ -377,20 +373,39 @@ int reftable_writer_add_logs(struct reftable_writer *w,
 
 static int writer_finish_section(struct reftable_writer *w)
 {
+	struct reftable_block_stats *bstats = NULL;
 	uint8_t typ = block_writer_type(w->block_writer);
 	uint64_t index_start = 0;
 	int max_level = 0;
-	int threshold = w->opts.unpadded ? 1 : 3;
+	size_t threshold = w->opts.unpadded ? 1 : 3;
 	int before_blocks = w->stats.idx_stats.blocks;
-	int err = writer_flush_block(w);
-	int i = 0;
-	struct reftable_block_stats *bstats = NULL;
+	int err;
+
+	err = writer_flush_block(w);
 	if (err < 0)
 		return err;
 
+	/*
+	 * When the section we are about to index has a lot of blocks then the
+	 * index itself may span across multiple blocks, as well. This would
+	 * require a linear scan over index blocks only to find the desired
+	 * indexed block, which is inefficient. Instead, we write a multi-level
+	 * index where index records of level N+1 will refer to index blocks of
+	 * level N. This isn't constant time, either, but at least logarithmic.
+	 *
+	 * This loop handles writing this multi-level index. Note that we write
+	 * the lowest-level index pointing to the indexed blocks first. We then
+	 * continue writing additional index levels until the current level has
+	 * less blocks than the threshold so that the highest level will be at
+	 * the end of the index section.
+	 *
+	 * Readers are thus required to start reading the index section from
+	 * its end, which is why we set `index_start` to the beginning of the
+	 * last index section.
+	 */
 	while (w->index_len > threshold) {
 		struct reftable_index_record *idx = NULL;
-		int idx_len = 0;
+		size_t i, idx_len;
 
 		max_level++;
 		index_start = w->next;
@@ -409,35 +424,28 @@ static int writer_finish_section(struct reftable_writer *w)
 					.idx = idx[i],
 				},
 			};
-			if (block_writer_add(w->block_writer, &rec) == 0) {
-				continue;
-			}
 
-			err = writer_flush_block(w);
+			err = writer_add_record(w, &rec);
 			if (err < 0)
 				return err;
-
-			writer_reinit_block_writer(w, BLOCK_TYPE_INDEX);
-
-			err = block_writer_add(w->block_writer, &rec);
-			if (err != 0) {
-				/* write into fresh block should always succeed
-				 */
-				abort();
-			}
 		}
-		for (i = 0; i < idx_len; i++) {
+
+		err = writer_flush_block(w);
+		if (err < 0)
+			return err;
+
+		for (i = 0; i < idx_len; i++)
 			strbuf_release(&idx[i].last_key);
-		}
 		reftable_free(idx);
 	}
 
+	/*
+	 * The index may still contain a number of index blocks lower than the
+	 * threshold. Clear it so that these entries don't leak into the next
+	 * index section.
+	 */
 	writer_clear_index(w);
 
-	err = writer_flush_block(w);
-	if (err < 0)
-		return err;
-
 	bstats = writer_reftable_block_stats(w, typ);
 	bstats->index_blocks = w->stats.idx_stats.blocks - before_blocks;
 	bstats->index_offset = index_start;
@@ -603,6 +611,12 @@ int reftable_writer_close(struct reftable_writer *w)
 	put_be32(p, crc32(0, footer, p - footer));
 	p += 4;
 
+	err = w->flush(w->write_arg);
+	if (err < 0) {
+		err = REFTABLE_IO_ERROR;
+		goto done;
+	}
+
 	err = padded_write(w, footer, footer_size(writer_version(w)), 0);
 	if (err < 0)
 		goto done;
@@ -622,11 +636,8 @@ int reftable_writer_close(struct reftable_writer *w)
 
 static void writer_clear_index(struct reftable_writer *w)
 {
-	int i = 0;
-	for (i = 0; i < w->index_len; i++) {
+	for (size_t i = 0; i < w->index_len; i++)
 		strbuf_release(&w->index[i].last_key);
-	}
-
 	FREE_AND_NULL(w->index);
 	w->index_len = 0;
 	w->index_cap = 0;
@@ -674,12 +685,7 @@ static int writer_flush_nonempty_block(struct reftable_writer *w)
 	if (err < 0)
 		return err;
 
-	if (w->index_cap == w->index_len) {
-		w->index_cap = 2 * w->index_cap + 1;
-		w->index = reftable_realloc(
-			w->index,
-			sizeof(struct reftable_index_record) * w->index_cap);
-	}
+	REFTABLE_ALLOC_GROW(w->index, w->index_len + 1, w->index_cap);
 
 	ir.offset = w->next;
 	strbuf_reset(&ir.last_key);
diff --git a/reftable/writer.h b/reftable/writer.h
index 09b8867..8d0df9c 100644
--- a/reftable/writer.h
+++ b/reftable/writer.h
@@ -16,6 +16,7 @@ license that can be found in the LICENSE file or at
 
 struct reftable_writer {
 	ssize_t (*write)(void *, const void *, size_t);
+	int (*flush)(void *);
 	void *write_arg;
 	int pending_padding;
 	struct strbuf last_key;
diff --git a/remote-curl.c b/remote-curl.c
index 7f81bf3..1161dc7 100644
--- a/remote-curl.c
+++ b/remote-curl.c
@@ -1446,8 +1446,14 @@ static int stateless_connect(const char *service_name)
 	 * establish a stateless connection, otherwise we need to tell the
 	 * client to fallback to using other transport helper functions to
 	 * complete their request.
+	 *
+	 * The "git-upload-archive" service is a read-only operation. Fallback
+	 * to use "git-upload-pack" service to discover protocol version.
 	 */
-	discover = discover_refs(service_name, 0);
+	if (!strcmp(service_name, "git-upload-archive"))
+		discover = discover_refs("git-upload-pack", 0);
+	else
+		discover = discover_refs(service_name, 0);
 	if (discover->version != protocol_v2) {
 		printf("fallback\n");
 		fflush(stdout);
@@ -1485,9 +1491,11 @@ static int stateless_connect(const char *service_name)
 
 	/*
 	 * Dump the capability listing that we got from the server earlier
-	 * during the info/refs request.
+	 * during the info/refs request. This does not work with the
+	 * "git-upload-archive" service.
 	 */
-	write_or_die(rpc.in, discover->buf, discover->len);
+	if (strcmp(service_name, "git-upload-archive"))
+		write_or_die(rpc.in, discover->buf, discover->len);
 
 	/* Until we see EOF keep sending POSTs */
 	while (1) {
@@ -1563,8 +1571,11 @@ int cmd_main(int argc, const char **argv)
 		if (buf.len == 0)
 			break;
 		if (starts_with(buf.buf, "fetch ")) {
-			if (nongit)
-				die(_("remote-curl: fetch attempted without a local repo"));
+			if (nongit) {
+				setup_git_directory_gently(&nongit);
+				if (nongit)
+					die(_("remote-curl: fetch attempted without a local repo"));
+			}
 			parse_fetch(&buf);
 
 		} else if (!strcmp(buf.buf, "list") || starts_with(buf.buf, "list ")) {
diff --git a/remote.c b/remote.c
index 6bef953..e07b316 100644
--- a/remote.c
+++ b/remote.c
@@ -508,7 +508,7 @@ static void alias_all_urls(struct remote_state *remote_state)
 	}
 }
 
-static void read_config(struct repository *repo)
+static void read_config(struct repository *repo, int early)
 {
 	int flag;
 
@@ -517,7 +517,7 @@ static void read_config(struct repository *repo)
 	repo->remote_state->initialized = 1;
 
 	repo->remote_state->current_branch = NULL;
-	if (startup_info->have_repository) {
+	if (startup_info->have_repository && !early) {
 		const char *head_ref = refs_resolve_ref_unsafe(
 			get_main_ref_store(repo), "HEAD", 0, NULL, &flag);
 		if (head_ref && (flag & REF_ISSYMREF) &&
@@ -560,7 +560,7 @@ static const char *remotes_remote_for_branch(struct remote_state *remote_state,
 
 const char *remote_for_branch(struct branch *branch, int *explicit)
 {
-	read_config(the_repository);
+	read_config(the_repository, 0);
 	die_on_missing_branch(the_repository, branch);
 
 	return remotes_remote_for_branch(the_repository->remote_state, branch,
@@ -586,7 +586,7 @@ remotes_pushremote_for_branch(struct remote_state *remote_state,
 
 const char *pushremote_for_branch(struct branch *branch, int *explicit)
 {
-	read_config(the_repository);
+	read_config(the_repository, 0);
 	die_on_missing_branch(the_repository, branch);
 
 	return remotes_pushremote_for_branch(the_repository->remote_state,
@@ -598,7 +598,7 @@ static struct remote *remotes_remote_get(struct remote_state *remote_state,
 
 const char *remote_ref_for_branch(struct branch *branch, int for_push)
 {
-	read_config(the_repository);
+	read_config(the_repository, 0);
 	die_on_missing_branch(the_repository, branch);
 
 	if (branch) {
@@ -708,7 +708,13 @@ remotes_remote_get(struct remote_state *remote_state, const char *name)
 
 struct remote *remote_get(const char *name)
 {
-	read_config(the_repository);
+	read_config(the_repository, 0);
+	return remotes_remote_get(the_repository->remote_state, name);
+}
+
+struct remote *remote_get_early(const char *name)
+{
+	read_config(the_repository, 1);
 	return remotes_remote_get(the_repository->remote_state, name);
 }
 
@@ -721,7 +727,7 @@ remotes_pushremote_get(struct remote_state *remote_state, const char *name)
 
 struct remote *pushremote_get(const char *name)
 {
-	read_config(the_repository);
+	read_config(the_repository, 0);
 	return remotes_pushremote_get(the_repository->remote_state, name);
 }
 
@@ -737,7 +743,7 @@ int remote_is_configured(struct remote *remote, int in_repo)
 int for_each_remote(each_remote_fn fn, void *priv)
 {
 	int i, result = 0;
-	read_config(the_repository);
+	read_config(the_repository, 0);
 	for (i = 0; i < the_repository->remote_state->remotes_nr && !result;
 	     i++) {
 		struct remote *remote =
@@ -1830,7 +1836,7 @@ struct branch *branch_get(const char *name)
 {
 	struct branch *ret;
 
-	read_config(the_repository);
+	read_config(the_repository, 0);
 	if (!name || !*name || !strcmp(name, "HEAD"))
 		ret = the_repository->remote_state->current_branch;
 	else
@@ -1972,7 +1978,7 @@ static const char *branch_get_push_1(struct remote_state *remote_state,
 
 const char *branch_get_push(struct branch *branch, struct strbuf *err)
 {
-	read_config(the_repository);
+	read_config(the_repository, 0);
 	die_on_missing_branch(the_repository, branch);
 
 	if (!branch)
diff --git a/remote.h b/remote.h
index 3a7377f..dfd4837 100644
--- a/remote.h
+++ b/remote.h
@@ -118,6 +118,7 @@ struct remote {
  * and configuration.
  */
 struct remote *remote_get(const char *name);
+struct remote *remote_get_early(const char *name);
 
 struct remote *pushremote_get(const char *name);
 int remote_is_configured(struct remote *remote, int in_repo);
diff --git a/repo-settings.c b/repo-settings.c
index 30cd478..a0b590b 100644
--- a/repo-settings.c
+++ b/repo-settings.c
@@ -43,6 +43,7 @@ void prepare_repo_settings(struct repository *r)
 	if (experimental) {
 		r->settings.fetch_negotiation_algorithm = FETCH_NEGOTIATION_SKIPPING;
 		r->settings.pack_use_bitmap_boundary_traversal = 1;
+		r->settings.pack_use_multi_pack_reuse = 1;
 	}
 	if (manyfiles) {
 		r->settings.index_version = 4;
diff --git a/repository.c b/repository.c
index a7679ce..7aacb51 100644
--- a/repository.c
+++ b/repository.c
@@ -104,6 +104,11 @@ void repo_set_hash_algo(struct repository *repo, int hash_algo)
 	repo->hash_algo = &hash_algos[hash_algo];
 }
 
+void repo_set_ref_storage_format(struct repository *repo, unsigned int format)
+{
+	repo->ref_storage_format = format;
+}
+
 /*
  * Attempt to resolve and set the provided 'gitdir' for repository 'repo'.
  * Return 0 upon success and a non-zero value upon failure.
@@ -184,6 +189,7 @@ int repo_init(struct repository *repo,
 		goto error;
 
 	repo_set_hash_algo(repo, format.hash_algo);
+	repo_set_ref_storage_format(repo, format.ref_storage_format);
 	repo->repository_format_worktree_config = format.worktree_config;
 
 	/* take ownership of format.partial_clone */
@@ -256,8 +262,6 @@ static void repo_clear_path_cache(struct repo_path_cache *cache)
 	FREE_AND_NULL(cache->merge_rr);
 	FREE_AND_NULL(cache->merge_mode);
 	FREE_AND_NULL(cache->merge_head);
-	FREE_AND_NULL(cache->merge_autostash);
-	FREE_AND_NULL(cache->auto_merge);
 	FREE_AND_NULL(cache->fetch_head);
 	FREE_AND_NULL(cache->shallow);
 }
diff --git a/repository.h b/repository.h
index 5f18486..21949c5 100644
--- a/repository.h
+++ b/repository.h
@@ -24,6 +24,9 @@ enum fetch_negotiation_setting {
 	FETCH_NEGOTIATION_NOOP,
 };
 
+#define REF_STORAGE_FORMAT_UNKNOWN 0
+#define REF_STORAGE_FORMAT_FILES   1
+
 struct repo_settings {
 	int initialized;
 
@@ -36,6 +39,7 @@ struct repo_settings {
 	int sparse_index;
 	int pack_read_reverse_index;
 	int pack_use_bitmap_boundary_traversal;
+	int pack_use_multi_pack_reuse;
 
 	/*
 	 * Does this repository have core.useReplaceRefs=true (on by
@@ -64,8 +68,6 @@ struct repo_path_cache {
 	char *merge_rr;
 	char *merge_mode;
 	char *merge_head;
-	char *merge_autostash;
-	char *auto_merge;
 	char *fetch_head;
 	char *shallow;
 };
@@ -160,6 +162,9 @@ struct repository {
 	/* Repository's current hash algorithm, as serialized on disk. */
 	const struct git_hash_algo *hash_algo;
 
+	/* Repository's reference storage format, as serialized on disk. */
+	unsigned int ref_storage_format;
+
 	/* A unique-id for tracing purposes. */
 	int trace2_repo_id;
 
@@ -199,6 +204,7 @@ void repo_set_gitdir(struct repository *repo, const char *root,
 		     const struct set_gitdir_args *extra_args);
 void repo_set_worktree(struct repository *repo, const char *path);
 void repo_set_hash_algo(struct repository *repo, int algo);
+void repo_set_ref_storage_format(struct repository *repo, unsigned int format);
 void initialize_the_repository(void);
 RESULT_MUST_BE_USED
 int repo_init(struct repository *r, const char *gitdir, const char *worktree);
diff --git a/sequencer.c b/sequencer.c
index 3cc88d8..91de546 100644
--- a/sequencer.c
+++ b/sequencer.c
@@ -474,7 +474,7 @@ static void print_advice(struct repository *r, int show_hint,
 		 * of the commit itself so remove CHERRY_PICK_HEAD
 		 */
 		refs_delete_ref(get_main_ref_store(r), "", "CHERRY_PICK_HEAD",
-				NULL, 0);
+				NULL, REF_NO_DEREF);
 		return;
 	}
 
@@ -1667,7 +1667,7 @@ static int do_commit(struct repository *r,
 		strbuf_release(&sb);
 		if (!res) {
 			refs_delete_ref(get_main_ref_store(r), "",
-					"CHERRY_PICK_HEAD", NULL, 0);
+					"CHERRY_PICK_HEAD", NULL, REF_NO_DEREF);
 			unlink(git_path_merge_msg(r));
 			if (!is_rebase_i(opts))
 				print_commit_summary(r, NULL, &oid,
@@ -2406,9 +2406,10 @@ static int do_pick_commit(struct repository *r,
 	} else if (allow == 2) {
 		drop_commit = 1;
 		refs_delete_ref(get_main_ref_store(r), "", "CHERRY_PICK_HEAD",
-				NULL, 0);
+				NULL, REF_NO_DEREF);
 		unlink(git_path_merge_msg(r));
-		unlink(git_path_auto_merge(r));
+		refs_delete_ref(get_main_ref_store(r), "", "AUTO_MERGE",
+				NULL, REF_NO_DEREF);
 		fprintf(stderr,
 			_("dropping %s %s -- patch contents already upstream\n"),
 			oid_to_hex(&commit->object.oid), msg.subject);
@@ -2802,7 +2803,7 @@ void sequencer_post_commit_cleanup(struct repository *r, int verbose)
 
 	if (refs_ref_exists(get_main_ref_store(r), "CHERRY_PICK_HEAD")) {
 		if (!refs_delete_ref(get_main_ref_store(r), "",
-				     "CHERRY_PICK_HEAD", NULL, 0) &&
+				     "CHERRY_PICK_HEAD", NULL, REF_NO_DEREF) &&
 		    verbose)
 			warning(_("cancelling a cherry picking in progress"));
 		opts.action = REPLAY_PICK;
@@ -2811,14 +2812,15 @@ void sequencer_post_commit_cleanup(struct repository *r, int verbose)
 
 	if (refs_ref_exists(get_main_ref_store(r), "REVERT_HEAD")) {
 		if (!refs_delete_ref(get_main_ref_store(r), "", "REVERT_HEAD",
-				     NULL, 0) &&
+				     NULL, REF_NO_DEREF) &&
 		    verbose)
 			warning(_("cancelling a revert in progress"));
 		opts.action = REPLAY_REVERT;
 		need_cleanup = 1;
 	}
 
-	unlink(git_path_auto_merge(r));
+	refs_delete_ref(get_main_ref_store(r), "", "AUTO_MERGE",
+			NULL, REF_NO_DEREF);
 
 	if (!need_cleanup)
 		return;
@@ -4116,7 +4118,7 @@ static int do_merge(struct repository *r,
 
 		strbuf_release(&ref_name);
 		refs_delete_ref(get_main_ref_store(r), "", "CHERRY_PICK_HEAD",
-				NULL, 0);
+				NULL, REF_NO_DEREF);
 		rollback_lock_file(&lock);
 
 		ret = run_command(&cmd);
@@ -4461,12 +4463,17 @@ static enum todo_command peek_command(struct todo_list *todo_list, int offset)
 	return -1;
 }
 
-void create_autostash(struct repository *r, const char *path)
+static void create_autostash_internal(struct repository *r,
+				      const char *path,
+				      const char *refname)
 {
 	struct strbuf buf = STRBUF_INIT;
 	struct lock_file lock_file = LOCK_INIT;
 	int fd;
 
+	if (path && refname)
+		BUG("can only pass path or refname");
+
 	fd = repo_hold_locked_index(r, &lock_file, 0);
 	refresh_index(r->index, REFRESH_QUIET, NULL, NULL, NULL);
 	if (0 <= fd)
@@ -4493,10 +4500,16 @@ void create_autostash(struct repository *r, const char *path)
 		strbuf_reset(&buf);
 		strbuf_add_unique_abbrev(&buf, &oid, DEFAULT_ABBREV);
 
-		if (safe_create_leading_directories_const(path))
-			die(_("Could not create directory for '%s'"),
-			    path);
-		write_file(path, "%s", oid_to_hex(&oid));
+		if (path) {
+			if (safe_create_leading_directories_const(path))
+				die(_("Could not create directory for '%s'"),
+				    path);
+			write_file(path, "%s", oid_to_hex(&oid));
+		} else {
+			refs_update_ref(get_main_ref_store(r), "", refname,
+					&oid, null_oid(), 0, UPDATE_REFS_DIE_ON_ERR);
+		}
+
 		printf(_("Created autostash: %s\n"), buf.buf);
 		if (reset_head(r, &ropts) < 0)
 			die(_("could not reset --hard"));
@@ -4507,6 +4520,16 @@ void create_autostash(struct repository *r, const char *path)
 	strbuf_release(&buf);
 }
 
+void create_autostash(struct repository *r, const char *path)
+{
+	create_autostash_internal(r, path, NULL);
+}
+
+void create_autostash_ref(struct repository *r, const char *refname)
+{
+	create_autostash_internal(r, NULL, refname);
+}
+
 static int apply_save_autostash_oid(const char *stash_oid, int attempt_apply)
 {
 	struct child_process child = CHILD_PROCESS_INIT;
@@ -4584,6 +4607,41 @@ int apply_autostash_oid(const char *stash_oid)
 	return apply_save_autostash_oid(stash_oid, 1);
 }
 
+static int apply_save_autostash_ref(struct repository *r, const char *refname,
+				    int attempt_apply)
+{
+	struct object_id stash_oid;
+	char stash_oid_hex[GIT_MAX_HEXSZ + 1];
+	int flag, ret;
+
+	if (!refs_ref_exists(get_main_ref_store(r), refname))
+		return 0;
+
+	if (!refs_resolve_ref_unsafe(get_main_ref_store(r), refname,
+				     RESOLVE_REF_READING, &stash_oid, &flag))
+		return -1;
+	if (flag & REF_ISSYMREF)
+		return error(_("autostash reference is a symref"));
+
+	oid_to_hex_r(stash_oid_hex, &stash_oid);
+	ret = apply_save_autostash_oid(stash_oid_hex, attempt_apply);
+
+	refs_delete_ref(get_main_ref_store(r), "", refname,
+			&stash_oid, REF_NO_DEREF);
+
+	return ret;
+}
+
+int save_autostash_ref(struct repository *r, const char *refname)
+{
+	return apply_save_autostash_ref(r, refname, 0);
+}
+
+int apply_autostash_ref(struct repository *r, const char *refname)
+{
+	return apply_save_autostash_ref(r, refname, 1);
+}
+
 static int checkout_onto(struct repository *r, struct replay_opts *opts,
 			 const char *onto_name, const struct object_id *onto,
 			 const struct object_id *orig_head)
@@ -4766,8 +4824,10 @@ static int pick_commits(struct repository *r,
 			}
 			unlink(rebase_path_author_script());
 			unlink(git_path_merge_head(r));
-			unlink(git_path_auto_merge(r));
-			delete_ref(NULL, "REBASE_HEAD", NULL, REF_NO_DEREF);
+			refs_delete_ref(get_main_ref_store(r), "", "AUTO_MERGE",
+					NULL, REF_NO_DEREF);
+			refs_delete_ref(get_main_ref_store(r), "", "REBASE_HEAD",
+					NULL, REF_NO_DEREF);
 
 			if (item->command == TODO_BREAK) {
 				if (!opts->verbose)
@@ -5108,7 +5168,7 @@ static int commit_staged_changes(struct repository *r,
 		if (refs_ref_exists(get_main_ref_store(r),
 				    "CHERRY_PICK_HEAD") &&
 		    refs_delete_ref(get_main_ref_store(r), "",
-				    "CHERRY_PICK_HEAD", NULL, 0))
+				    "CHERRY_PICK_HEAD", NULL, REF_NO_DEREF))
 			return error(_("could not remove CHERRY_PICK_HEAD"));
 		if (unlink(git_path_merge_msg(r)) && errno != ENOENT)
 			return error_errno(_("could not remove '%s'"),
@@ -5122,7 +5182,8 @@ static int commit_staged_changes(struct repository *r,
 		return error(_("could not commit staged changes."));
 	unlink(rebase_path_amend());
 	unlink(git_path_merge_head(r));
-	unlink(git_path_auto_merge(r));
+	refs_delete_ref(get_main_ref_store(r), "", "AUTO_MERGE",
+			NULL, REF_NO_DEREF);
 	if (final_fixup) {
 		unlink(rebase_path_fixup_msg());
 		unlink(rebase_path_squash_msg());
diff --git a/sequencer.h b/sequencer.h
index 913a0f6..dcef7bb 100644
--- a/sequencer.h
+++ b/sequencer.h
@@ -225,9 +225,12 @@ void commit_post_rewrite(struct repository *r,
 			 const struct object_id *new_head);
 
 void create_autostash(struct repository *r, const char *path);
+void create_autostash_ref(struct repository *r, const char *refname);
 int save_autostash(const char *path);
+int save_autostash_ref(struct repository *r, const char *refname);
 int apply_autostash(const char *path);
 int apply_autostash_oid(const char *stash_oid);
+int apply_autostash_ref(struct repository *r, const char *refname);
 
 #define SUMMARY_INITIAL_COMMIT   (1 << 0)
 #define SUMMARY_SHOW_AUTHOR_DATE (1 << 1)
diff --git a/setup.c b/setup.c
index 75df669..b69b1cb 100644
--- a/setup.c
+++ b/setup.c
@@ -591,6 +591,17 @@ static enum extension_result handle_extension(const char *var,
 				     "extensions.objectformat", value);
 		data->hash_algo = format;
 		return EXTENSION_OK;
+	} else if (!strcmp(ext, "refstorage")) {
+		unsigned int format;
+
+		if (!value)
+			return config_error_nonbool(var);
+		format = ref_storage_format_by_name(value);
+		if (format == REF_STORAGE_FORMAT_UNKNOWN)
+			return error(_("invalid value for '%s': '%s'"),
+				     "extensions.refstorage", value);
+		data->ref_storage_format = format;
+		return EXTENSION_OK;
 	}
 	return EXTENSION_UNKNOWN;
 }
@@ -1360,7 +1371,8 @@ static enum discovery_result setup_git_directory_gently_1(struct strbuf *dir,
 
 		if (is_git_directory(dir->buf)) {
 			trace2_data_string("setup", NULL, "implicit-bare-repository", dir->buf);
-			if (get_allowed_bare_repo() == ALLOWED_BARE_REPO_EXPLICIT)
+			if (get_allowed_bare_repo() == ALLOWED_BARE_REPO_EXPLICIT &&
+			    !ends_with_path_components(dir->buf, ".git"))
 				return GIT_DIR_DISALLOWED_BARE;
 			if (!ensure_valid_ownership(NULL, NULL, dir->buf, report))
 				return GIT_DIR_INVALID_OWNERSHIP;
@@ -1565,6 +1577,8 @@ const char *setup_git_directory_gently(int *nongit_ok)
 		}
 		if (startup_info->have_repository) {
 			repo_set_hash_algo(the_repository, repo_fmt.hash_algo);
+			repo_set_ref_storage_format(the_repository,
+						    repo_fmt.ref_storage_format);
 			the_repository->repository_format_worktree_config =
 				repo_fmt.worktree_config;
 			/* take ownership of repo_fmt.partial_clone */
@@ -1658,6 +1672,8 @@ void check_repository_format(struct repository_format *fmt)
 	check_repository_format_gently(get_git_dir(), fmt, NULL);
 	startup_info->have_repository = 1;
 	repo_set_hash_algo(the_repository, fmt->hash_algo);
+	repo_set_ref_storage_format(the_repository,
+				    fmt->ref_storage_format);
 	the_repository->repository_format_worktree_config =
 		fmt->worktree_config;
 	the_repository->repository_format_partial_clone =
@@ -1866,12 +1882,15 @@ static int needs_work_tree_config(const char *git_dir, const char *work_tree)
 	return 1;
 }
 
-void initialize_repository_version(int hash_algo, int reinit)
+void initialize_repository_version(int hash_algo,
+				   unsigned int ref_storage_format,
+				   int reinit)
 {
 	char repo_version_string[10];
 	int repo_version = GIT_REPO_VERSION;
 
-	if (hash_algo != GIT_HASH_SHA1)
+	if (hash_algo != GIT_HASH_SHA1 ||
+	    ref_storage_format != REF_STORAGE_FORMAT_FILES)
 		repo_version = GIT_REPO_VERSION_READ;
 
 	/* This forces creation of new config file */
@@ -1884,23 +1903,72 @@ void initialize_repository_version(int hash_algo, int reinit)
 			       hash_algos[hash_algo].name);
 	else if (reinit)
 		git_config_set_gently("extensions.objectformat", NULL);
+
+	if (ref_storage_format != REF_STORAGE_FORMAT_FILES)
+		git_config_set("extensions.refstorage",
+			       ref_storage_format_to_name(ref_storage_format));
+}
+
+static int is_reinit(void)
+{
+	struct strbuf buf = STRBUF_INIT;
+	char junk[2];
+	int ret;
+
+	git_path_buf(&buf, "HEAD");
+	ret = !access(buf.buf, R_OK) || readlink(buf.buf, junk, sizeof(junk) - 1) != -1;
+	strbuf_release(&buf);
+	return ret;
+}
+
+void create_reference_database(unsigned int ref_storage_format,
+			       const char *initial_branch, int quiet)
+{
+	struct strbuf err = STRBUF_INIT;
+	int reinit = is_reinit();
+
+	repo_set_ref_storage_format(the_repository, ref_storage_format);
+	if (refs_init_db(get_main_ref_store(the_repository), 0, &err))
+		die("failed to set up refs db: %s", err.buf);
+
+	/*
+	 * Point the HEAD symref to the initial branch with if HEAD does
+	 * not yet exist.
+	 */
+	if (!reinit) {
+		char *ref;
+
+		if (!initial_branch)
+			initial_branch = git_default_branch_name(quiet);
+
+		ref = xstrfmt("refs/heads/%s", initial_branch);
+		if (check_refname_format(ref, 0) < 0)
+			die(_("invalid initial branch name: '%s'"),
+			    initial_branch);
+
+		if (create_symref("HEAD", ref, NULL) < 0)
+			exit(1);
+		free(ref);
+	}
+
+	if (reinit && initial_branch)
+		warning(_("re-init: ignored --initial-branch=%s"),
+			initial_branch);
+
+	strbuf_release(&err);
 }
 
 static int create_default_files(const char *template_path,
 				const char *original_git_dir,
-				const char *initial_branch,
 				const struct repository_format *fmt,
 				int prev_bare_repository,
-				int init_shared_repository,
-				int quiet)
+				int init_shared_repository)
 {
 	struct stat st1;
 	struct strbuf buf = STRBUF_INIT;
 	char *path;
-	char junk[2];
 	int reinit;
 	int filemode;
-	struct strbuf err = STRBUF_INIT;
 	const char *init_template_dir = NULL;
 	const char *work_tree = get_git_work_tree();
 
@@ -1920,6 +1988,8 @@ static int create_default_files(const char *template_path,
 	reset_shared_repository();
 	git_config(git_default_config, NULL);
 
+	reinit = is_reinit();
+
 	/*
 	 * We must make sure command-line options continue to override any
 	 * values we might have just re-read from the config.
@@ -1963,40 +2033,7 @@ static int create_default_files(const char *template_path,
 		adjust_shared_perm(get_git_dir());
 	}
 
-	/*
-	 * We need to create a "refs" dir in any case so that older
-	 * versions of git can tell that this is a repository.
-	 */
-	safe_create_dir(git_path("refs"), 1);
-	adjust_shared_perm(git_path("refs"));
-
-	if (refs_init_db(&err))
-		die("failed to set up refs db: %s", err.buf);
-
-	/*
-	 * Point the HEAD symref to the initial branch with if HEAD does
-	 * not yet exist.
-	 */
-	path = git_path_buf(&buf, "HEAD");
-	reinit = (!access(path, R_OK)
-		  || readlink(path, junk, sizeof(junk)-1) != -1);
-	if (!reinit) {
-		char *ref;
-
-		if (!initial_branch)
-			initial_branch = git_default_branch_name(quiet);
-
-		ref = xstrfmt("refs/heads/%s", initial_branch);
-		if (check_refname_format(ref, 0) < 0)
-			die(_("invalid initial branch name: '%s'"),
-			    initial_branch);
-
-		if (create_symref("HEAD", ref, NULL) < 0)
-			exit(1);
-		free(ref);
-	}
-
-	initialize_repository_version(fmt->hash_algo, 0);
+	initialize_repository_version(fmt->hash_algo, fmt->ref_storage_format, 0);
 
 	/* Check filemode trustability */
 	path = git_path_buf(&buf, "config");
@@ -2109,8 +2146,29 @@ static void validate_hash_algorithm(struct repository_format *repo_fmt, int hash
 	}
 }
 
+static void validate_ref_storage_format(struct repository_format *repo_fmt,
+					unsigned int format)
+{
+	const char *name = getenv("GIT_DEFAULT_REF_FORMAT");
+
+	if (repo_fmt->version >= 0 &&
+	    format != REF_STORAGE_FORMAT_UNKNOWN &&
+	    format != repo_fmt->ref_storage_format) {
+		die(_("attempt to reinitialize repository with different reference storage format"));
+	} else if (format != REF_STORAGE_FORMAT_UNKNOWN) {
+		repo_fmt->ref_storage_format = format;
+	} else if (name) {
+		format = ref_storage_format_by_name(name);
+		if (format == REF_STORAGE_FORMAT_UNKNOWN)
+			die(_("unknown ref storage format '%s'"), name);
+		repo_fmt->ref_storage_format = format;
+	}
+}
+
 int init_db(const char *git_dir, const char *real_git_dir,
-	    const char *template_dir, int hash, const char *initial_branch,
+	    const char *template_dir, int hash,
+	    unsigned int ref_storage_format,
+	    const char *initial_branch,
 	    int init_shared_repository, unsigned int flags)
 {
 	int reinit;
@@ -2153,16 +2211,22 @@ int init_db(const char *git_dir, const char *real_git_dir,
 	check_repository_format(&repo_fmt);
 
 	validate_hash_algorithm(&repo_fmt, hash);
+	validate_ref_storage_format(&repo_fmt, ref_storage_format);
 
 	reinit = create_default_files(template_dir, original_git_dir,
-				      initial_branch, &repo_fmt,
-				      prev_bare_repository,
-				      init_shared_repository,
-				      flags & INIT_DB_QUIET);
-	if (reinit && initial_branch)
-		warning(_("re-init: ignored --initial-branch=%s"),
-			initial_branch);
+				      &repo_fmt, prev_bare_repository,
+				      init_shared_repository);
 
+	/*
+	 * Now that we have set up both the hash algorithm and the ref storage
+	 * format we can update the repository's settings accordingly.
+	 */
+	repo_set_hash_algo(the_repository, repo_fmt.hash_algo);
+	repo_set_ref_storage_format(the_repository, repo_fmt.ref_storage_format);
+
+	if (!(flags & INIT_DB_SKIP_REFDB))
+		create_reference_database(repo_fmt.ref_storage_format,
+					  initial_branch, flags & INIT_DB_QUIET);
 	create_object_directory();
 
 	if (get_shared_repository()) {
diff --git a/setup.h b/setup.h
index b48cf1c..3599aec 100644
--- a/setup.h
+++ b/setup.h
@@ -115,6 +115,7 @@ struct repository_format {
 	int worktree_config;
 	int is_bare;
 	int hash_algo;
+	unsigned int ref_storage_format;
 	int sparse_index;
 	char *work_tree;
 	struct string_list unknown_extensions;
@@ -131,6 +132,7 @@ struct repository_format {
 	.version = -1, \
 	.is_bare = -1, \
 	.hash_algo = GIT_HASH_SHA1, \
+	.ref_storage_format = REF_STORAGE_FORMAT_FILES, \
 	.unknown_extensions = STRING_LIST_INIT_DUP, \
 	.v1_only_extensions = STRING_LIST_INIT_DUP, \
 }
@@ -169,14 +171,20 @@ int verify_repository_format(const struct repository_format *format,
  */
 void check_repository_format(struct repository_format *fmt);
 
-#define INIT_DB_QUIET 0x0001
-#define INIT_DB_EXIST_OK 0x0002
+#define INIT_DB_QUIET      (1 << 0)
+#define INIT_DB_EXIST_OK   (1 << 1)
+#define INIT_DB_SKIP_REFDB (1 << 2)
 
 int init_db(const char *git_dir, const char *real_git_dir,
 	    const char *template_dir, int hash_algo,
+	    unsigned int ref_storage_format,
 	    const char *initial_branch, int init_shared_repository,
 	    unsigned int flags);
-void initialize_repository_version(int hash_algo, int reinit);
+void initialize_repository_version(int hash_algo,
+				   unsigned int ref_storage_format,
+				   int reinit);
+void create_reference_database(unsigned int ref_storage_format,
+			       const char *initial_branch, int quiet);
 
 /*
  * NOTE NOTE NOTE!!
diff --git a/shared.mak b/shared.mak
index aeb80fc..29bebd3 100644
--- a/shared.mak
+++ b/shared.mak
@@ -108,3 +108,11 @@
 define mkdir_p_parent_template
 $(if $(wildcard $(@D)),,$(QUIET_MKDIR_P_PARENT)$(shell mkdir -p $(@D)))
 endef
+
+## Getting sick of writing -L$(SOMELIBDIR) $(CC_LD_DYNPATH)$(SOMELIBDIR)?
+## Write $(call libpath_template,$(SOMELIBDIR)) instead, perhaps?
+## With CC_LD_DYNPATH set to either an empty string or to "-L", the
+## the directory is not shown the second time.
+define libpath_template
+-L$(1) $(if $(filter-out -L,$(CC_LD_DYNPATH)),$(CC_LD_DYNPATH)$(1))
+endef
diff --git a/sparse-index.c b/sparse-index.c
index 3578feb..e48e40c 100644
--- a/sparse-index.c
+++ b/sparse-index.c
@@ -579,8 +579,9 @@ void expand_to_path(struct index_state *istate,
 		replace++;
 		temp = *replace;
 		*replace = '\0';
+		substr_len = replace - path_mutable.buf;
 		if (index_file_exists(istate, path_mutable.buf,
-				      path_mutable.len, icase)) {
+				      substr_len, icase)) {
 			/*
 			 * We found a parent directory in the name-hash
 			 * hashtable, because only sparse directory entries
@@ -593,7 +594,6 @@ void expand_to_path(struct index_state *istate,
 		}
 
 		*replace = temp;
-		substr_len = replace - path_mutable.buf;
 	}
 
 cleanup:
diff --git a/statinfo.c b/statinfo.c
index 9367ca0..3c6bc04 100644
--- a/statinfo.c
+++ b/statinfo.c
@@ -31,6 +31,33 @@ void fill_stat_data(struct stat_data *sd, struct stat *st)
 	sd->sd_size = munge_st_size(st->st_size);
 }
 
+static void set_times(struct stat *st, const struct stat_data *sd)
+{
+	st->st_ctime = sd->sd_ctime.sec;
+	st->st_mtime = sd->sd_mtime.sec;
+#ifdef NO_NSEC
+	; /* nothing */
+#else
+#ifdef USE_ST_TIMESPEC
+	st->st_ctimespec.tv_nsec = sd->sd_ctime.nsec;
+	st->st_mtimespec.tv_nsec = sd->sd_mtime.nsec;
+#else
+	st->st_ctim.tv_nsec = sd->sd_ctime.nsec;
+	st->st_mtim.tv_nsec = sd->sd_mtime.nsec;
+#endif
+#endif
+}
+
+void fake_lstat_data(const struct stat_data *sd, struct stat *st)
+{
+	set_times(st, sd);
+	st->st_dev = sd->sd_dev;
+	st->st_ino = sd->sd_ino;
+	st->st_uid = sd->sd_uid;
+	st->st_gid = sd->sd_gid;
+	st->st_size = sd->sd_size;
+}
+
 int match_stat_data(const struct stat_data *sd, struct stat *st)
 {
 	int changed = 0;
diff --git a/statinfo.h b/statinfo.h
index 700f502..5b21a30 100644
--- a/statinfo.h
+++ b/statinfo.h
@@ -47,6 +47,14 @@ struct stat_validity {
 void fill_stat_data(struct stat_data *sd, struct stat *st);
 
 /*
+ * The inverse of the above.  When we know the cache_entry that
+ * contains sd is up-to-date, but still need to pretend we called
+ * lstat() to learn that fact, this function fills "st" enough to
+ * fool ie_match_stat().
+ */
+void fake_lstat_data(const struct stat_data *sd, struct stat *st);
+
+/*
  * Return 0 if st is consistent with a file not having been changed
  * since sd was filled.  If there are differences, return a
  * combination of MTIME_CHANGED, CTIME_CHANGED, OWNER_CHANGED,
diff --git a/submodule-config.c b/submodule-config.c
index f4dd482..54130f6 100644
--- a/submodule-config.c
+++ b/submodule-config.c
@@ -14,6 +14,8 @@
 #include "parse-options.h"
 #include "thread-utils.h"
 #include "tree-walk.h"
+#include "url.h"
+#include "urlmatch.h"
 
 /*
  * submodule cache lookup structure
@@ -228,6 +230,144 @@ int check_submodule_name(const char *name)
 	return 0;
 }
 
+static int starts_with_dot_slash(const char *const path)
+{
+	return path_match_flags(path, PATH_MATCH_STARTS_WITH_DOT_SLASH |
+				PATH_MATCH_XPLATFORM);
+}
+
+static int starts_with_dot_dot_slash(const char *const path)
+{
+	return path_match_flags(path, PATH_MATCH_STARTS_WITH_DOT_DOT_SLASH |
+				PATH_MATCH_XPLATFORM);
+}
+
+static int submodule_url_is_relative(const char *url)
+{
+	return starts_with_dot_slash(url) || starts_with_dot_dot_slash(url);
+}
+
+/*
+ * Count directory components that a relative submodule URL should chop
+ * from the remote_url it is to be resolved against.
+ *
+ * In other words, this counts "../" components at the start of a
+ * submodule URL.
+ *
+ * Returns the number of directory components to chop and writes a
+ * pointer to the next character of url after all leading "./" and
+ * "../" components to out.
+ */
+static int count_leading_dotdots(const char *url, const char **out)
+{
+	int result = 0;
+	while (1) {
+		if (starts_with_dot_dot_slash(url)) {
+			result++;
+			url += strlen("../");
+			continue;
+		}
+		if (starts_with_dot_slash(url)) {
+			url += strlen("./");
+			continue;
+		}
+		*out = url;
+		return result;
+	}
+}
+/*
+ * Check whether a transport is implemented by git-remote-curl.
+ *
+ * If it is, returns 1 and writes the URL that would be passed to
+ * git-remote-curl to the "out" parameter.
+ *
+ * Otherwise, returns 0 and leaves "out" untouched.
+ *
+ * Examples:
+ *   http::https://example.com/repo.git -> 1, https://example.com/repo.git
+ *   https://example.com/repo.git -> 1, https://example.com/repo.git
+ *   git://example.com/repo.git -> 0
+ *
+ * This is for use in checking for previously exploitable bugs that
+ * required a submodule URL to be passed to git-remote-curl.
+ */
+static int url_to_curl_url(const char *url, const char **out)
+{
+	/*
+	 * We don't need to check for case-aliases, "http.exe", and so
+	 * on because in the default configuration, is_transport_allowed
+	 * prevents URLs with those schemes from being cloned
+	 * automatically.
+	 */
+	if (skip_prefix(url, "http::", out) ||
+	    skip_prefix(url, "https::", out) ||
+	    skip_prefix(url, "ftp::", out) ||
+	    skip_prefix(url, "ftps::", out))
+		return 1;
+	if (starts_with(url, "http://") ||
+	    starts_with(url, "https://") ||
+	    starts_with(url, "ftp://") ||
+	    starts_with(url, "ftps://")) {
+		*out = url;
+		return 1;
+	}
+	return 0;
+}
+
+int check_submodule_url(const char *url)
+{
+	const char *curl_url;
+
+	if (looks_like_command_line_option(url))
+		return -1;
+
+	if (submodule_url_is_relative(url) || starts_with(url, "git://")) {
+		char *decoded;
+		const char *next;
+		int has_nl;
+
+		/*
+		 * This could be appended to an http URL and url-decoded;
+		 * check for malicious characters.
+		 */
+		decoded = url_decode(url);
+		has_nl = !!strchr(decoded, '\n');
+
+		free(decoded);
+		if (has_nl)
+			return -1;
+
+		/*
+		 * URLs which escape their root via "../" can overwrite
+		 * the host field and previous components, resolving to
+		 * URLs like https::example.com/submodule.git and
+		 * https:///example.com/submodule.git that were
+		 * susceptible to CVE-2020-11008.
+		 */
+		if (count_leading_dotdots(url, &next) > 0 &&
+		    (*next == ':' || *next == '/'))
+			return -1;
+	}
+
+	else if (url_to_curl_url(url, &curl_url)) {
+		int ret = 0;
+		char *normalized = url_normalize(curl_url, NULL);
+		if (normalized) {
+			char *decoded = url_decode(normalized);
+			if (strchr(decoded, '\n'))
+				ret = -1;
+			free(normalized);
+			free(decoded);
+		} else {
+			ret = -1;
+		}
+
+		return ret;
+	}
+
+	return 0;
+}
+
 static int name_and_item_from_var(const char *var, struct strbuf *name,
 				  struct strbuf *item)
 {
diff --git a/submodule-config.h b/submodule-config.h
index 958f320..b6133af 100644
--- a/submodule-config.h
+++ b/submodule-config.h
@@ -89,6 +89,9 @@ int config_set_in_gitmodules_file_gently(const char *key, const char *value);
  */
 int check_submodule_name(const char *name);
 
+/* Returns 0 if the URL valid per RFC3986 and -1 otherwise. */
+int check_submodule_url(const char *url);
+
 /*
  * Note: these helper functions exist solely to maintain backward
  * compatibility with 'fetch' and 'update_clone' storing configuration in
diff --git a/t/Makefile b/t/Makefile
index fae3012..2d95046 100644
--- a/t/Makefile
+++ b/t/Makefile
@@ -1,3 +1,6 @@
+# The default target of this Makefile is...
+all::
+
 # Import tree-wide shared Makefile behavior and libraries
 include ../shared.mak
 
@@ -6,6 +9,7 @@
 # Copyright (c) 2005 Junio C Hamano
 #
 
+-include ../config.mak.uname
 -include ../config.mak.autogen
 -include ../config.mak
 
@@ -17,6 +21,7 @@
 RM ?= rm -f
 PROVE ?= prove
 DEFAULT_TEST_TARGET ?= test
+DEFAULT_UNIT_TEST_TARGET ?= unit-tests-raw
 TEST_LINT ?= test-lint
 
 ifdef TEST_OUTPUT_DIRECTORY
@@ -41,13 +46,16 @@
 TINTEROP = $(sort $(wildcard interop/i[0-9][0-9][0-9][0-9]-*.sh))
 CHAINLINTTESTS = $(sort $(patsubst chainlint/%.test,%,$(wildcard chainlint/*.test)))
 CHAINLINT = '$(PERL_PATH_SQ)' chainlint.pl
+UNIT_TEST_SOURCES = $(wildcard unit-tests/t-*.c)
+UNIT_TEST_PROGRAMS = $(patsubst unit-tests/%.c,unit-tests/bin/%$(X),$(UNIT_TEST_SOURCES))
+UNIT_TESTS = $(sort $(filter-out unit-tests/bin/t-basic%,$(UNIT_TEST_PROGRAMS)))
 
 # `test-chainlint` (which is a dependency of `test-lint`, `test` and `prove`)
 # checks all tests in all scripts via a single invocation, so tell individual
 # scripts not to run the external "chainlint.pl" script themselves
 CHAINLINTSUPPRESS = GIT_TEST_EXT_CHAIN_LINT=0 && export GIT_TEST_EXT_CHAIN_LINT &&
 
-all: $(DEFAULT_TEST_TARGET)
+all:: $(DEFAULT_TEST_TARGET)
 
 test: pre-clean check-chainlint $(TEST_LINT)
 	$(CHAINLINTSUPPRESS) $(MAKE) aggregate-results-and-cleanup
@@ -65,6 +73,17 @@
 $(T):
 	@echo "*** $@ ***"; '$(TEST_SHELL_PATH_SQ)' $@ $(GIT_TEST_OPTS)
 
+$(UNIT_TESTS):
+	@echo "*** $@ ***"; $@
+
+.PHONY: unit-tests unit-tests-raw unit-tests-prove
+unit-tests: $(DEFAULT_UNIT_TEST_TARGET)
+
+unit-tests-raw: $(UNIT_TESTS)
+
+unit-tests-prove:
+	@echo "*** prove - unit tests ***"; $(PROVE) $(GIT_PROVE_OPTS) $(UNIT_TESTS)
+
 pre-clean:
 	$(RM) -r '$(TEST_RESULTS_DIRECTORY_SQ)'
 
@@ -141,4 +160,4 @@
 	$(MAKE) -C perf/ all
 
 .PHONY: pre-clean $(T) aggregate-results clean valgrind perf \
-	check-chainlint clean-chainlint test-chainlint
+	check-chainlint clean-chainlint test-chainlint $(UNIT_TESTS)
diff --git a/t/README b/t/README
index 36463d0..621d3b8 100644
--- a/t/README
+++ b/t/README
@@ -479,6 +479,9 @@
 use in the test scripts. Recognized values for <hash-algo> are "sha1"
 and "sha256".
 
+GIT_TEST_DEFAULT_REF_FORMAT=<format> specifies which ref storage format
+to use in the test scripts. Recognized values for <format> are "files".
+
 GIT_TEST_NO_WRITE_REV_INDEX=<boolean>, when true disables the
 'pack.writeReverseIndex' setting.
 
diff --git a/t/helper/test-ctype.c b/t/helper/test-ctype.c
deleted file mode 100644
index e5659df..0000000
--- a/t/helper/test-ctype.c
+++ /dev/null
@@ -1,70 +0,0 @@
-#include "test-tool.h"
-
-static int rc;
-
-static void report_error(const char *class, int ch)
-{
-	printf("%s classifies char %d (0x%02x) wrongly\n", class, ch, ch);
-	rc = 1;
-}
-
-static int is_in(const char *s, int ch)
-{
-	/*
-	 * We can't find NUL using strchr. Accept it as the first
-	 * character in the spec -- there are no empty classes.
-	 */
-	if (ch == '\0')
-		return ch == *s;
-	if (*s == '\0')
-		s++;
-	return !!strchr(s, ch);
-}
-
-#define TEST_CLASS(t,s) {			\
-	int i;					\
-	for (i = 0; i < 256; i++) {		\
-		if (is_in(s, i) != t(i))	\
-			report_error(#t, i);	\
-	}					\
-	if (t(EOF))				\
-		report_error(#t, EOF);		\
-}
-
-#define DIGIT "0123456789"
-#define LOWER "abcdefghijklmnopqrstuvwxyz"
-#define UPPER "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
-#define PUNCT "!\"#$%&'()*+,-./:;<=>?@[\\]^_`{|}~"
-#define ASCII \
-	"\x00\x01\x02\x03\x04\x05\x06\x07\x08\x09\x0a\x0b\x0c\x0d\x0e\x0f" \
-	"\x10\x11\x12\x13\x14\x15\x16\x17\x18\x19\x1a\x1b\x1c\x1d\x1e\x1f" \
-	"\x20\x21\x22\x23\x24\x25\x26\x27\x28\x29\x2a\x2b\x2c\x2d\x2e\x2f" \
-	"\x30\x31\x32\x33\x34\x35\x36\x37\x38\x39\x3a\x3b\x3c\x3d\x3e\x3f" \
-	"\x40\x41\x42\x43\x44\x45\x46\x47\x48\x49\x4a\x4b\x4c\x4d\x4e\x4f" \
-	"\x50\x51\x52\x53\x54\x55\x56\x57\x58\x59\x5a\x5b\x5c\x5d\x5e\x5f" \
-	"\x60\x61\x62\x63\x64\x65\x66\x67\x68\x69\x6a\x6b\x6c\x6d\x6e\x6f" \
-	"\x70\x71\x72\x73\x74\x75\x76\x77\x78\x79\x7a\x7b\x7c\x7d\x7e\x7f"
-#define CNTRL \
-	"\x00\x01\x02\x03\x04\x05\x06\x07\x08\x09\x0a\x0b\x0c\x0d\x0e\x0f" \
-	"\x10\x11\x12\x13\x14\x15\x16\x17\x18\x19\x1a\x1b\x1c\x1d\x1e\x1f" \
-	"\x7f"
-
-int cmd__ctype(int argc UNUSED, const char **argv UNUSED)
-{
-	TEST_CLASS(isdigit, DIGIT);
-	TEST_CLASS(isspace, " \n\r\t");
-	TEST_CLASS(isalpha, LOWER UPPER);
-	TEST_CLASS(isalnum, LOWER UPPER DIGIT);
-	TEST_CLASS(is_glob_special, "*?[\\");
-	TEST_CLASS(is_regex_special, "$()*+.?[\\^{|");
-	TEST_CLASS(is_pathspec_magic, "!\"#%&',-/:;<=>@_`~");
-	TEST_CLASS(isascii, ASCII);
-	TEST_CLASS(islower, LOWER);
-	TEST_CLASS(isupper, UPPER);
-	TEST_CLASS(iscntrl, CNTRL);
-	TEST_CLASS(ispunct, PUNCT);
-	TEST_CLASS(isxdigit, DIGIT "abcdefABCDEF");
-	TEST_CLASS(isprint, LOWER UPPER DIGIT PUNCT " ");
-
-	return rc;
-}
diff --git a/t/helper/test-fast-rebase.c b/t/helper/test-fast-rebase.c
deleted file mode 100644
index cac20a7..0000000
--- a/t/helper/test-fast-rebase.c
+++ /dev/null
@@ -1,241 +0,0 @@
-/*
- * "git fast-rebase" builtin command
- *
- * FAST: Forking Any Subprocesses (is) Taboo
- *
- * This is meant SOLELY as a demo of what is possible.  sequencer.c and
- * rebase.c should be refactored to use the ideas here, rather than attempting
- * to extend this file to replace those (unless Phillip or Dscho say that
- * refactoring is too hard and we need a clean slate, but I'm guessing that
- * refactoring is the better route).
- */
-
-#define USE_THE_INDEX_VARIABLE
-#include "test-tool.h"
-#include "cache-tree.h"
-#include "commit.h"
-#include "environment.h"
-#include "gettext.h"
-#include "hash.h"
-#include "hex.h"
-#include "lockfile.h"
-#include "merge-ort.h"
-#include "object-name.h"
-#include "read-cache-ll.h"
-#include "refs.h"
-#include "revision.h"
-#include "sequencer.h"
-#include "setup.h"
-#include "strvec.h"
-#include "tree.h"
-
-static const char *short_commit_name(struct commit *commit)
-{
-	return repo_find_unique_abbrev(the_repository, &commit->object.oid,
-				       DEFAULT_ABBREV);
-}
-
-static struct commit *peel_committish(const char *name)
-{
-	struct object *obj;
-	struct object_id oid;
-
-	if (repo_get_oid(the_repository, name, &oid))
-		return NULL;
-	obj = parse_object(the_repository, &oid);
-	return (struct commit *)repo_peel_to_type(the_repository, name, 0, obj,
-						  OBJ_COMMIT);
-}
-
-static char *get_author(const char *message)
-{
-	size_t len;
-	const char *a;
-
-	a = find_commit_header(message, "author", &len);
-	if (a)
-		return xmemdupz(a, len);
-
-	return NULL;
-}
-
-static struct commit *create_commit(struct tree *tree,
-				    struct commit *based_on,
-				    struct commit *parent)
-{
-	struct object_id ret;
-	struct object *obj;
-	struct commit_list *parents = NULL;
-	char *author;
-	char *sign_commit = NULL;
-	struct commit_extra_header *extra;
-	struct strbuf msg = STRBUF_INIT;
-	const char *out_enc = get_commit_output_encoding();
-	const char *message = repo_logmsg_reencode(the_repository, based_on,
-						   NULL, out_enc);
-	const char *orig_message = NULL;
-	const char *exclude_gpgsig[] = { "gpgsig", NULL };
-
-	commit_list_insert(parent, &parents);
-	extra = read_commit_extra_headers(based_on, exclude_gpgsig);
-	find_commit_subject(message, &orig_message);
-	strbuf_addstr(&msg, orig_message);
-	author = get_author(message);
-	reset_ident_date();
-	if (commit_tree_extended(msg.buf, msg.len, &tree->object.oid, parents,
-				 &ret, author, NULL, sign_commit, extra)) {
-		error(_("failed to write commit object"));
-		return NULL;
-	}
-	free(author);
-	strbuf_release(&msg);
-
-	obj = parse_object(the_repository, &ret);
-	return (struct commit *)obj;
-}
-
-int cmd__fast_rebase(int argc, const char **argv)
-{
-	struct commit *onto;
-	struct commit *last_commit = NULL, *last_picked_commit = NULL;
-	struct object_id head;
-	struct lock_file lock = LOCK_INIT;
-	struct strvec rev_walk_args = STRVEC_INIT;
-	struct rev_info revs;
-	struct commit *commit;
-	struct merge_options merge_opt;
-	struct tree *next_tree, *base_tree, *head_tree;
-	struct merge_result result;
-	struct strbuf reflog_msg = STRBUF_INIT;
-	struct strbuf branch_name = STRBUF_INIT;
-	int ret = 0;
-
-	/*
-	 * test-tool stuff doesn't set up the git directory by default; need to
-	 * do that manually.
-	 */
-	setup_git_directory();
-
-	if (argc == 2 && !strcmp(argv[1], "-h")) {
-		printf("Sorry, I am not a psychiatrist; I can not give you the help you need.  Oh, you meant usage...\n");
-		exit(129);
-	}
-
-	if (argc != 5 || strcmp(argv[1], "--onto"))
-		die("usage: read the code, figure out how to use it, then do so");
-
-	onto = peel_committish(argv[2]);
-	strbuf_addf(&branch_name, "refs/heads/%s", argv[4]);
-
-	/* Sanity check */
-	if (repo_get_oid(the_repository, "HEAD", &head))
-		die(_("Cannot read HEAD"));
-	assert(oideq(&onto->object.oid, &head));
-
-	repo_hold_locked_index(the_repository, &lock, LOCK_DIE_ON_ERROR);
-	if (repo_read_index(the_repository) < 0)
-		BUG("Could not read index");
-
-	repo_init_revisions(the_repository, &revs, NULL);
-	revs.verbose_header = 1;
-	revs.max_parents = 1;
-	revs.cherry_mark = 1;
-	revs.limited = 1;
-	revs.reverse = 1;
-	revs.right_only = 1;
-	revs.sort_order = REV_SORT_IN_GRAPH_ORDER;
-	revs.topo_order = 1;
-	strvec_pushl(&rev_walk_args, "", argv[4], "--not", argv[3], NULL);
-
-	if (setup_revisions(rev_walk_args.nr, rev_walk_args.v, &revs, NULL) > 1) {
-		ret = error(_("unhandled options"));
-		goto cleanup;
-	}
-
-	strvec_clear(&rev_walk_args);
-
-	if (prepare_revision_walk(&revs) < 0) {
-		ret = error(_("error preparing revisions"));
-		goto cleanup;
-	}
-
-	init_merge_options(&merge_opt, the_repository);
-	memset(&result, 0, sizeof(result));
-	merge_opt.show_rename_progress = 1;
-	merge_opt.branch1 = "HEAD";
-	head_tree = repo_get_commit_tree(the_repository, onto);
-	result.tree = head_tree;
-	last_commit = onto;
-	while ((commit = get_revision(&revs))) {
-		struct commit *base;
-
-		fprintf(stderr, "Rebasing %s...\r",
-			oid_to_hex(&commit->object.oid));
-		assert(commit->parents && !commit->parents->next);
-		base = commit->parents->item;
-
-		next_tree = repo_get_commit_tree(the_repository, commit);
-		base_tree = repo_get_commit_tree(the_repository, base);
-
-		merge_opt.branch2 = short_commit_name(commit);
-		merge_opt.ancestor = xstrfmt("parent of %s", merge_opt.branch2);
-
-		merge_incore_nonrecursive(&merge_opt,
-					  base_tree,
-					  result.tree,
-					  next_tree,
-					  &result);
-
-		free((char*)merge_opt.ancestor);
-		merge_opt.ancestor = NULL;
-		if (!result.clean)
-			break;
-		last_picked_commit = commit;
-		last_commit = create_commit(result.tree, commit, last_commit);
-	}
-
-	merge_switch_to_result(&merge_opt, head_tree, &result, 1, !result.clean);
-
-	if (result.clean < 0)
-		exit(128);
-
-	if (result.clean) {
-		fprintf(stderr, "\nDone.\n");
-		strbuf_addf(&reflog_msg, "finish rebase %s onto %s",
-			    oid_to_hex(&last_picked_commit->object.oid),
-			    oid_to_hex(&last_commit->object.oid));
-		if (update_ref(reflog_msg.buf, branch_name.buf,
-			       &last_commit->object.oid,
-			       &last_picked_commit->object.oid,
-			       REF_NO_DEREF, UPDATE_REFS_MSG_ON_ERR)) {
-			error(_("could not update %s"), argv[4]);
-			die("Failed to update %s", argv[4]);
-		}
-		if (create_symref("HEAD", branch_name.buf, reflog_msg.buf) < 0)
-			die(_("unable to update HEAD"));
-
-		prime_cache_tree(the_repository, the_repository->index,
-				 result.tree);
-	} else {
-		fprintf(stderr, "\nAborting: Hit a conflict.\n");
-		strbuf_addf(&reflog_msg, "rebase progress up to %s",
-			    oid_to_hex(&last_picked_commit->object.oid));
-		if (update_ref(reflog_msg.buf, "HEAD",
-			       &last_commit->object.oid,
-			       &head,
-			       REF_NO_DEREF, UPDATE_REFS_MSG_ON_ERR)) {
-			error(_("could not update %s"), argv[4]);
-			die("Failed to update %s", argv[4]);
-		}
-	}
-	if (write_locked_index(&the_index, &lock,
-			       COMMIT_LOCK | SKIP_IF_UNCHANGED))
-		die(_("unable to write %s"), get_index_file());
-
-	ret = (result.clean == 0);
-cleanup:
-	strbuf_release(&reflog_msg);
-	strbuf_release(&branch_name);
-	release_revisions(&revs);
-	return ret;
-}
diff --git a/t/helper/test-prio-queue.c b/t/helper/test-prio-queue.c
deleted file mode 100644
index f0bf255..0000000
--- a/t/helper/test-prio-queue.c
+++ /dev/null
@@ -1,51 +0,0 @@
-#include "test-tool.h"
-#include "prio-queue.h"
-
-static int intcmp(const void *va, const void *vb, void *data UNUSED)
-{
-	const int *a = va, *b = vb;
-	return *a - *b;
-}
-
-static void show(int *v)
-{
-	if (!v)
-		printf("NULL\n");
-	else
-		printf("%d\n", *v);
-	free(v);
-}
-
-int cmd__prio_queue(int argc UNUSED, const char **argv)
-{
-	struct prio_queue pq = { intcmp };
-
-	while (*++argv) {
-		if (!strcmp(*argv, "get")) {
-			void *peek = prio_queue_peek(&pq);
-			void *get = prio_queue_get(&pq);
-			if (peek != get)
-				BUG("peek and get results do not match");
-			show(get);
-		} else if (!strcmp(*argv, "dump")) {
-			void *peek;
-			void *get;
-			while ((peek = prio_queue_peek(&pq))) {
-				get = prio_queue_get(&pq);
-				if (peek != get)
-					BUG("peek and get results do not match");
-				show(get);
-			}
-		} else if (!strcmp(*argv, "stack")) {
-			pq.compare = NULL;
-		} else {
-			int *v = xmalloc(sizeof(*v));
-			*v = atoi(*argv);
-			prio_queue_put(&pq, v);
-		}
-	}
-
-	clear_prio_queue(&pq);
-
-	return 0;
-}
diff --git a/t/helper/test-read-midx.c b/t/helper/test-read-midx.c
index e9a444d..4acae41 100644
--- a/t/helper/test-read-midx.c
+++ b/t/helper/test-read-midx.c
@@ -6,6 +6,7 @@
 #include "pack-bitmap.h"
 #include "packfile.h"
 #include "setup.h"
+#include "gettext.h"
 
 static int read_midx_file(const char *object_dir, int show_objects)
 {
@@ -79,7 +80,7 @@ static int read_midx_checksum(const char *object_dir)
 static int read_midx_preferred_pack(const char *object_dir)
 {
 	struct multi_pack_index *midx = NULL;
-	struct bitmap_index *bitmap = NULL;
+	uint32_t preferred_pack;
 
 	setup_git_directory();
 
@@ -87,23 +88,45 @@ static int read_midx_preferred_pack(const char *object_dir)
 	if (!midx)
 		return 1;
 
-	bitmap = prepare_bitmap_git(the_repository);
-	if (!bitmap)
-		return 1;
-	if (!bitmap_is_midx(bitmap)) {
-		free_bitmap_index(bitmap);
+	if (midx_preferred_pack(midx, &preferred_pack) < 0) {
+		warning(_("could not determine MIDX preferred pack"));
 		return 1;
 	}
 
-	printf("%s\n", midx->pack_names[midx_preferred_pack(bitmap)]);
-	free_bitmap_index(bitmap);
+	printf("%s\n", midx->pack_names[preferred_pack]);
+	return 0;
+}
+
+static int read_midx_bitmapped_packs(const char *object_dir)
+{
+	struct multi_pack_index *midx = NULL;
+	struct bitmapped_pack pack;
+	uint32_t i;
+
+	setup_git_directory();
+
+	midx = load_multi_pack_index(object_dir, 1);
+	if (!midx)
+		return 1;
+
+	for (i = 0; i < midx->num_packs; i++) {
+		if (nth_bitmapped_pack(the_repository, midx, &pack, i) < 0)
+			return 1;
+
+		printf("%s\n", pack_basename(pack.p));
+		printf("  bitmap_pos: %"PRIuMAX"\n", (uintmax_t)pack.bitmap_pos);
+		printf("  bitmap_nr: %"PRIuMAX"\n", (uintmax_t)pack.bitmap_nr);
+	}
+
+	close_midx(midx);
+
 	return 0;
 }
 
 int cmd__read_midx(int argc, const char **argv)
 {
 	if (!(argc == 2 || argc == 3))
-		usage("read-midx [--show-objects|--checksum|--preferred-pack] <object-dir>");
+		usage("read-midx [--show-objects|--checksum|--preferred-pack|--bitmap] <object-dir>");
 
 	if (!strcmp(argv[1], "--show-objects"))
 		return read_midx_file(argv[2], 1);
@@ -111,5 +134,7 @@ int cmd__read_midx(int argc, const char **argv)
 		return read_midx_checksum(argv[2]);
 	else if (!strcmp(argv[1], "--preferred-pack"))
 		return read_midx_preferred_pack(argv[2]);
+	else if (!strcmp(argv[1], "--bitmap"))
+		return read_midx_bitmapped_packs(argv[2]);
 	return read_midx_file(argv[1], 0);
 }
diff --git a/t/helper/test-ref-store.c b/t/helper/test-ref-store.c
index 48552e6..702ec1f 100644
--- a/t/helper/test-ref-store.c
+++ b/t/helper/test-ref-store.c
@@ -298,16 +298,19 @@ static int cmd_update_ref(struct ref_store *refs, const char **argv)
 	const char *new_sha1_buf = notnull(*argv++, "new-sha1");
 	const char *old_sha1_buf = notnull(*argv++, "old-sha1");
 	unsigned int flags = arg_flags(*argv++, "flags", transaction_flags);
-	struct object_id old_oid;
+	struct object_id old_oid, *old_oid_ptr = NULL;
 	struct object_id new_oid;
 
-	if (get_oid_hex(old_sha1_buf, &old_oid))
-		die("cannot parse %s as %s", old_sha1_buf, the_hash_algo->name);
+	if (*old_sha1_buf) {
+		if (get_oid_hex(old_sha1_buf, &old_oid))
+			die("cannot parse %s as %s", old_sha1_buf, the_hash_algo->name);
+		old_oid_ptr = &old_oid;
+	}
 	if (get_oid_hex(new_sha1_buf, &new_oid))
 		die("cannot parse %s as %s", new_sha1_buf, the_hash_algo->name);
 
 	return refs_update_ref(refs, msg, refname,
-			       &new_oid, &old_oid,
+			       &new_oid, old_oid_ptr,
 			       flags, UPDATE_REFS_DIE_ON_ERR);
 }
 
diff --git a/t/helper/test-submodule.c b/t/helper/test-submodule.c
index 50c154d..7197969 100644
--- a/t/helper/test-submodule.c
+++ b/t/helper/test-submodule.c
@@ -9,12 +9,19 @@
 #include "submodule.h"
 
 #define TEST_TOOL_CHECK_NAME_USAGE \
-	"test-tool submodule check-name <name>"
+	"test-tool submodule check-name"
 static const char *submodule_check_name_usage[] = {
 	TEST_TOOL_CHECK_NAME_USAGE,
 	NULL
 };
 
+#define TEST_TOOL_CHECK_URL_USAGE \
+	"test-tool submodule check-url"
+static const char *submodule_check_url_usage[] = {
+	TEST_TOOL_CHECK_URL_USAGE,
+	NULL
+};
+
 #define TEST_TOOL_IS_ACTIVE_USAGE \
 	"test-tool submodule is-active <name>"
 static const char *submodule_is_active_usage[] = {
@@ -31,31 +38,26 @@ static const char *submodule_resolve_relative_url_usage[] = {
 
 static const char *submodule_usage[] = {
 	TEST_TOOL_CHECK_NAME_USAGE,
+	TEST_TOOL_CHECK_URL_USAGE,
 	TEST_TOOL_IS_ACTIVE_USAGE,
 	TEST_TOOL_RESOLVE_RELATIVE_URL_USAGE,
 	NULL
 };
 
+typedef int (*check_fn_t)(const char *);
+
 /*
- * Exit non-zero if any of the submodule names given on the command line is
- * invalid. If no names are given, filter stdin to print only valid names
- * (which is primarily intended for testing).
+ * Apply 'check_fn' to each line of stdin, printing values that pass the check
+ * to stdout.
  */
-static int check_name(int argc, const char **argv)
+static int check_submodule(check_fn_t check_fn)
 {
-	if (argc > 1) {
-		while (*++argv) {
-			if (check_submodule_name(*argv) < 0)
-				return 1;
-		}
-	} else {
-		struct strbuf buf = STRBUF_INIT;
-		while (strbuf_getline(&buf, stdin) != EOF) {
-			if (!check_submodule_name(buf.buf))
-				printf("%s\n", buf.buf);
-		}
-		strbuf_release(&buf);
+	struct strbuf buf = STRBUF_INIT;
+	while (strbuf_getline(&buf, stdin) != EOF) {
+		if (!check_fn(buf.buf))
+			printf("%s\n", buf.buf);
 	}
+	strbuf_release(&buf);
 	return 0;
 }
 
@@ -69,7 +71,20 @@ static int cmd__submodule_check_name(int argc, const char **argv)
 	if (argc)
 		usage_with_options(submodule_check_name_usage, options);
 
-	return check_name(argc, argv);
+	return check_submodule(check_submodule_name);
+}
+
+static int cmd__submodule_check_url(int argc, const char **argv)
+{
+	struct option options[] = {
+		OPT_END()
+	};
+	argc = parse_options(argc, argv, "test-tools", options,
+			     submodule_check_url_usage, 0);
+	if (argc)
+		usage_with_options(submodule_check_url_usage, options);
+
+	return check_submodule(check_submodule_url);
 }
 
 static int cmd__submodule_is_active(int argc, const char **argv)
@@ -195,6 +210,7 @@ static int cmd__submodule_config_writeable(int argc, const char **argv UNUSED)
 
 static struct test_cmd cmds[] = {
 	{ "check-name", cmd__submodule_check_name },
+	{ "check-url", cmd__submodule_check_url },
 	{ "is-active", cmd__submodule_is_active },
 	{ "resolve-relative-url", cmd__submodule_resolve_relative_url},
 	{ "config-list", cmd__submodule_config_list },
diff --git a/t/helper/test-tool.c b/t/helper/test-tool.c
index 876cd2d..482a1e5 100644
--- a/t/helper/test-tool.c
+++ b/t/helper/test-tool.c
@@ -19,7 +19,6 @@ static struct test_cmd cmds[] = {
 	{ "config", cmd__config },
 	{ "crontab", cmd__crontab },
 	{ "csprng", cmd__csprng },
-	{ "ctype", cmd__ctype },
 	{ "date", cmd__date },
 	{ "delta", cmd__delta },
 	{ "dir-iterator", cmd__dir_iterator },
@@ -30,7 +29,6 @@ static struct test_cmd cmds[] = {
 	{ "dump-untracked-cache", cmd__dump_untracked_cache },
 	{ "env-helper", cmd__env_helper },
 	{ "example-decorate", cmd__example_decorate },
-	{ "fast-rebase", cmd__fast_rebase },
 	{ "find-pack", cmd__find_pack },
 	{ "fsmonitor-client", cmd__fsmonitor_client },
 	{ "genrandom", cmd__genrandom },
@@ -57,7 +55,6 @@ static struct test_cmd cmds[] = {
 	{ "path-utils", cmd__path_utils },
 	{ "pcre2-config", cmd__pcre2_config },
 	{ "pkt-line", cmd__pkt_line },
-	{ "prio-queue", cmd__prio_queue },
 	{ "proc-receive", cmd__proc_receive },
 	{ "progress", cmd__progress },
 	{ "reach", cmd__reach },
diff --git a/t/helper/test-tool.h b/t/helper/test-tool.h
index 70dd4eb..b1be7cf 100644
--- a/t/helper/test-tool.h
+++ b/t/helper/test-tool.h
@@ -12,7 +12,6 @@ int cmd__chmtime(int argc, const char **argv);
 int cmd__config(int argc, const char **argv);
 int cmd__crontab(int argc, const char **argv);
 int cmd__csprng(int argc, const char **argv);
-int cmd__ctype(int argc, const char **argv);
 int cmd__date(int argc, const char **argv);
 int cmd__delta(int argc, const char **argv);
 int cmd__dir_iterator(int argc, const char **argv);
@@ -24,7 +23,6 @@ int cmd__dump_untracked_cache(int argc, const char **argv);
 int cmd__dump_reftable(int argc, const char **argv);
 int cmd__env_helper(int argc, const char **argv);
 int cmd__example_decorate(int argc, const char **argv);
-int cmd__fast_rebase(int argc, const char **argv);
 int cmd__find_pack(int argc, const char **argv);
 int cmd__fsmonitor_client(int argc, const char **argv);
 int cmd__genrandom(int argc, const char **argv);
@@ -50,7 +48,6 @@ int cmd__partial_clone(int argc, const char **argv);
 int cmd__path_utils(int argc, const char **argv);
 int cmd__pcre2_config(int argc, const char **argv);
 int cmd__pkt_line(int argc, const char **argv);
-int cmd__prio_queue(int argc, const char **argv);
 int cmd__proc_receive(int argc, const char **argv);
 int cmd__progress(int argc, const char **argv);
 int cmd__reach(int argc, const char **argv);
diff --git a/t/lib-httpd.sh b/t/lib-httpd.sh
index dbc9977..d83bafe 100644
--- a/t/lib-httpd.sh
+++ b/t/lib-httpd.sh
@@ -55,22 +55,31 @@
 
 HTTPD_PARA=""
 
-for DEFAULT_HTTPD_PATH in '/usr/sbin/httpd' '/usr/sbin/apache2'
+for DEFAULT_HTTPD_PATH in '/usr/sbin/httpd' \
+			  '/usr/sbin/apache2' \
+			  "$(command -v httpd)" \
+			  "$(command -v apache2)"
 do
-	if test -x "$DEFAULT_HTTPD_PATH"
+	if test -n "$DEFAULT_HTTPD_PATH" && test -x "$DEFAULT_HTTPD_PATH"
 	then
 		break
 	fi
 done
 
+if test -x "$DEFAULT_HTTPD_PATH"
+then
+	DETECTED_HTTPD_ROOT="$("$DEFAULT_HTTPD_PATH" -V 2>/dev/null | sed -n 's/^ -D HTTPD_ROOT="\(.*\)"$/\1/p')"
+fi
+
 for DEFAULT_HTTPD_MODULE_PATH in '/usr/libexec/apache2' \
 				 '/usr/lib/apache2/modules' \
 				 '/usr/lib64/httpd/modules' \
 				 '/usr/lib/httpd/modules' \
 				 '/usr/libexec/httpd' \
-				 '/usr/lib/apache2'
+				 '/usr/lib/apache2' \
+				 "${DETECTED_HTTPD_ROOT:+${DETECTED_HTTPD_ROOT}/modules}"
 do
-	if test -d "$DEFAULT_HTTPD_MODULE_PATH"
+	if test -n "$DEFAULT_HTTPD_MODULE_PATH" && test -d "$DEFAULT_HTTPD_MODULE_PATH"
 	then
 		break
 	fi
diff --git a/t/lib-httpd/passwd b/t/lib-httpd/passwd
index 99a34d6..d9c122f 100644
--- a/t/lib-httpd/passwd
+++ b/t/lib-httpd/passwd
@@ -1 +1 @@
-user@host:xb4E8pqD81KQs
+user@host:$apr1$LGPmCZWj$9vxEwj5Z5GzQLBMxp3mCx1
diff --git a/t/lib-httpd/proxy-passwd b/t/lib-httpd/proxy-passwd
index 77c2513..2ad7705 100644
--- a/t/lib-httpd/proxy-passwd
+++ b/t/lib-httpd/proxy-passwd
@@ -1 +1 @@
-proxuser:2x7tAukjAED5M
+proxuser:$apr1$RxS6MLkD$DYsqQdflheq4GPNxzJpx5.
diff --git a/t/perf/p5332-multi-pack-reuse.sh b/t/perf/p5332-multi-pack-reuse.sh
new file mode 100755
index 0000000..5c6c575
--- /dev/null
+++ b/t/perf/p5332-multi-pack-reuse.sh
@@ -0,0 +1,81 @@
+#!/bin/sh
+
+test_description='tests pack performance with multi-pack reuse'
+
+. ./perf-lib.sh
+. "${TEST_DIRECTORY}/perf/lib-pack.sh"
+
+packdir=.git/objects/pack
+
+test_perf_large_repo
+
+find_pack () {
+	for idx in $packdir/pack-*.idx
+	do
+		if git show-index <$idx | grep -q "$1"
+		then
+			basename $idx
+		fi || return 1
+	done
+}
+
+repack_into_n_chunks () {
+	git repack -adk &&
+
+	test "$1" -eq 1 && return ||
+
+	find $packdir -type f | sort >packs.before &&
+
+	# partition the repository into $1 chunks of consecutive commits, and
+	# then create $1 packs with the objects reachable from each chunk
+	# (excluding any objects reachable from the previous chunks)
+	sz="$(($(git rev-list --count --all) / $1))"
+	for rev in $(git rev-list --all | awk "NR % $sz == 0" | tac)
+	do
+		pack="$(echo "$rev" | git pack-objects --revs \
+			--honor-pack-keep --delta-base-offset $packdir/pack)" &&
+		touch $packdir/pack-$pack.keep || return 1
+	done
+
+	# grab any remaining objects not packed by the previous step(s)
+	git pack-objects --revs --all --honor-pack-keep --delta-base-offset \
+		$packdir/pack &&
+
+	find $packdir -type f | sort >packs.after &&
+
+	# and install the whole thing
+	for f in $(comm -12 packs.before packs.after)
+	do
+		rm -f "$f" || return 1
+	done
+	rm -fr $packdir/*.keep
+}
+
+for nr_packs in 1 10 100
+do
+	test_expect_success "create $nr_packs-pack scenario" '
+		repack_into_n_chunks $nr_packs
+	'
+
+	test_expect_success "setup bitmaps for $nr_packs-pack scenario" '
+		find $packdir -type f -name "*.idx" | sed -e "s/.*\/\(.*\)$/+\1/g" |
+		git multi-pack-index write --stdin-packs --bitmap \
+			--preferred-pack="$(find_pack $(git rev-parse HEAD))"
+	'
+
+	for reuse in single multi
+	do
+		test_perf "clone for $nr_packs-pack scenario ($reuse-pack reuse)" "
+			git for-each-ref --format='%(objectname)' refs/heads refs/tags >in &&
+			git -c pack.allowPackReuse=$reuse pack-objects \
+				--revs --delta-base-offset --use-bitmap-index \
+				--stdout <in >result
+		"
+
+		test_size "clone size for $nr_packs-pack scenario ($reuse-pack reuse)" '
+			wc -c <result
+		'
+	done
+done
+
+test_done
diff --git a/t/perf/p6300-for-each-ref.sh b/t/perf/p6300-for-each-ref.sh
new file mode 100755
index 0000000..fa7289c
--- /dev/null
+++ b/t/perf/p6300-for-each-ref.sh
@@ -0,0 +1,87 @@
+#!/bin/sh
+
+test_description='performance of for-each-ref'
+. ./perf-lib.sh
+
+test_perf_fresh_repo
+
+ref_count_per_type=10000
+test_iteration_count=10
+
+test_expect_success "setup" '
+	test_commit_bulk $(( 1 + $ref_count_per_type )) &&
+
+	# Create refs
+	test_seq $ref_count_per_type |
+		sed "s,.*,update refs/heads/branch_& HEAD~&\nupdate refs/custom/special_& HEAD~&," |
+		git update-ref --stdin &&
+
+	# Create annotated tags
+	for i in $(test_seq $ref_count_per_type)
+	do
+		# Base tags
+		echo "tag tag_$i" &&
+		echo "mark :$i" &&
+		echo "from HEAD~$i" &&
+		printf "tagger %s <%s> %s\n" \
+			"$GIT_COMMITTER_NAME" \
+			"$GIT_COMMITTER_EMAIL" \
+			"$GIT_COMMITTER_DATE" &&
+		echo "data <<EOF" &&
+		echo "tag $i" &&
+		echo "EOF" &&
+
+		# Nested tags
+		echo "tag nested_$i" &&
+		echo "from :$i" &&
+		printf "tagger %s <%s> %s\n" \
+			"$GIT_COMMITTER_NAME" \
+			"$GIT_COMMITTER_EMAIL" \
+			"$GIT_COMMITTER_DATE" &&
+		echo "data <<EOF" &&
+		echo "nested tag $i" &&
+		echo "EOF" || return 1
+	done | git fast-import
+'
+
+test_for_each_ref () {
+	title="for-each-ref"
+	if test $# -gt 0; then
+		title="$title ($1)"
+		shift
+	fi
+	args="$@"
+
+	test_perf "$title" "
+		for i in \$(test_seq $test_iteration_count); do
+			git for-each-ref $args >/dev/null
+		done
+	"
+}
+
+run_tests () {
+	test_for_each_ref "$1"
+	test_for_each_ref "$1, no sort" --no-sort
+	test_for_each_ref "$1, --count=1" --count=1
+	test_for_each_ref "$1, --count=1, no sort" --no-sort --count=1
+	test_for_each_ref "$1, tags" refs/tags/
+	test_for_each_ref "$1, tags, no sort" --no-sort refs/tags/
+	test_for_each_ref "$1, tags, dereferenced" '--format="%(refname) %(objectname) %(*objectname)"' refs/tags/
+	test_for_each_ref "$1, tags, dereferenced, no sort" --no-sort '--format="%(refname) %(objectname) %(*objectname)"' refs/tags/
+
+	test_perf "for-each-ref ($1, tags) + cat-file --batch-check (dereferenced)" "
+		for i in \$(test_seq $test_iteration_count); do
+			git for-each-ref --format='%(objectname)^{} %(refname) %(objectname)' refs/tags/ | \
+				git cat-file --batch-check='%(objectname) %(rest)' >/dev/null
+		done
+	"
+}
+
+run_tests "loose"
+
+test_expect_success 'pack refs' '
+	git pack-refs --all
+'
+run_tests "packed"
+
+test_done
diff --git a/t/perf/perf-lib.sh b/t/perf/perf-lib.sh
index def22e7..ab0c763 100644
--- a/t/perf/perf-lib.sh
+++ b/t/perf/perf-lib.sh
@@ -31,7 +31,7 @@
 GIT_CONFIG_SYSTEM="$TEST_DIRECTORY/perf/config"
 export GIT_CONFIG_SYSTEM
 
-if test -n "$GIT_TEST_INSTALLED" -a -z "$PERF_SET_GIT_TEST_INSTALLED"
+if test -n "$GIT_TEST_INSTALLED" && test -z "$PERF_SET_GIT_TEST_INSTALLED"
 then
 	error "Do not use GIT_TEST_INSTALLED with the perf tests.
 
diff --git a/t/perf/run b/t/perf/run
index 34115ed..486ead2 100755
--- a/t/perf/run
+++ b/t/perf/run
@@ -91,10 +91,10 @@
 run_dirs_helper () {
 	mydir=${1%/}
 	shift
-	while test $# -gt 0 -a "$1" != -- -a ! -f "$1"; do
+	while test $# -gt 0 && test "$1" != -- && test ! -f "$1"; do
 		shift
 	done
-	if test $# -gt 0 -a "$1" = --; then
+	if test $# -gt 0 && test "$1" = --; then
 		shift
 	fi
 
@@ -124,7 +124,7 @@
 }
 
 run_dirs () {
-	while test $# -gt 0 -a "$1" != -- -a ! -f "$1"; do
+	while test $# -gt 0 && test "$1" != -- && test ! -f "$1"; do
 		run_dirs_helper "$@"
 		shift
 	done
@@ -180,7 +180,8 @@
 	GIT_PERF_AGGREGATING_LATER=t
 	export GIT_PERF_AGGREGATING_LATER
 
-	if test $# = 0 -o "$1" = -- -o -f "$1"; then
+	if test $# = 0 || test "$1" = -- || test -f "$1"
+	then
 		set -- . "$@"
 	fi
 
diff --git a/t/t0001-init.sh b/t/t0001-init.sh
index 2b78e3b..b131d66 100755
--- a/t/t0001-init.sh
+++ b/t/t0001-init.sh
@@ -532,6 +532,76 @@
 	test_must_fail git -C sha256 init --object-format=sha1
 '
 
+test_expect_success DEFAULT_REPO_FORMAT 'extensions.refStorage is not allowed with repo version 0' '
+	test_when_finished "rm -rf refstorage" &&
+	git init refstorage &&
+	git -C refstorage config extensions.refStorage files &&
+	test_must_fail git -C refstorage rev-parse 2>err &&
+	grep "repo version is 0, but v1-only extension found" err
+'
+
+test_expect_success DEFAULT_REPO_FORMAT 'extensions.refStorage with files backend' '
+	test_when_finished "rm -rf refstorage" &&
+	git init refstorage &&
+	git -C refstorage config core.repositoryformatversion 1 &&
+	git -C refstorage config extensions.refStorage files &&
+	test_commit -C refstorage A &&
+	git -C refstorage rev-parse --verify HEAD
+'
+
+test_expect_success DEFAULT_REPO_FORMAT 'extensions.refStorage with unknown backend' '
+	test_when_finished "rm -rf refstorage" &&
+	git init refstorage &&
+	git -C refstorage config core.repositoryformatversion 1 &&
+	git -C refstorage config extensions.refStorage garbage &&
+	test_must_fail git -C refstorage rev-parse 2>err &&
+	grep "invalid value for ${SQ}extensions.refstorage${SQ}: ${SQ}garbage${SQ}" err
+'
+
+test_expect_success DEFAULT_REPO_FORMAT 'init with GIT_DEFAULT_REF_FORMAT=files' '
+	test_when_finished "rm -rf refformat" &&
+	GIT_DEFAULT_REF_FORMAT=files git init refformat &&
+	echo 0 >expect &&
+	git -C refformat config core.repositoryformatversion >actual &&
+	test_cmp expect actual &&
+	test_must_fail git -C refformat config extensions.refstorage
+'
+
+test_expect_success 'init with GIT_DEFAULT_REF_FORMAT=garbage' '
+	test_when_finished "rm -rf refformat" &&
+	cat >expect <<-EOF &&
+	fatal: unknown ref storage format ${SQ}garbage${SQ}
+	EOF
+	test_must_fail env GIT_DEFAULT_REF_FORMAT=garbage git init refformat 2>err &&
+	test_cmp expect err
+'
+
+test_expect_success 'init with --ref-format=files' '
+	test_when_finished "rm -rf refformat" &&
+	git init --ref-format=files refformat &&
+	echo files >expect &&
+	git -C refformat rev-parse --show-ref-format >actual &&
+	test_cmp expect actual
+'
+
+test_expect_success 're-init with same format' '
+	test_when_finished "rm -rf refformat" &&
+	git init --ref-format=files refformat &&
+	git init --ref-format=files refformat &&
+	echo files >expect &&
+	git -C refformat rev-parse --show-ref-format >actual &&
+	test_cmp expect actual
+'
+
+test_expect_success 'init with --ref-format=garbage' '
+	test_when_finished "rm -rf refformat" &&
+	cat >expect <<-EOF &&
+	fatal: unknown ref storage format ${SQ}garbage${SQ}
+	EOF
+	test_must_fail git init --ref-format=garbage refformat 2>err &&
+	test_cmp expect err
+'
+
 test_expect_success MINGW 'core.hidedotfiles = false' '
 	git config --global core.hidedotfiles false &&
 	rm -rf newdir &&
diff --git a/t/t0003-attributes.sh b/t/t0003-attributes.sh
index aee2298..774b52c 100755
--- a/t/t0003-attributes.sh
+++ b/t/t0003-attributes.sh
@@ -19,6 +19,20 @@
 	test_must_be_empty err
 }
 
+attr_check_object_mode_basic () {
+	path="$1" &&
+	expect="$2" &&
+	check_opts="$3" &&
+	git check-attr $check_opts builtin_objectmode -- "$path" >actual 2>err &&
+	echo "$path: builtin_objectmode: $expect" >expect &&
+	test_cmp expect actual
+}
+
+attr_check_object_mode () {
+	attr_check_object_mode_basic "$@" &&
+	test_must_be_empty err
+}
+
 attr_check_quote () {
 	path="$1" quoted_path="$2" expect="$3" &&
 
@@ -558,4 +572,66 @@
 	test_cmp expect err
 '
 
+test_expect_success 'builtin object mode attributes work (dir and regular paths)' '
+	>normal &&
+	attr_check_object_mode normal 100644 &&
+	mkdir dir &&
+	attr_check_object_mode dir 040000
+'
+
+test_expect_success POSIXPERM 'builtin object mode attributes work (executable)' '
+	>exec &&
+	chmod +x exec &&
+	attr_check_object_mode exec 100755
+'
+
+test_expect_success SYMLINKS 'builtin object mode attributes work (symlinks)' '
+	ln -s to_sym sym &&
+	attr_check_object_mode sym 120000
+'
+
+test_expect_success 'native object mode attributes work with --cached' '
+	>normal &&
+	git add normal &&
+	empty_blob=$(git rev-parse :normal) &&
+	git update-index --index-info <<-EOF &&
+	100755 $empty_blob 0	exec
+	120000 $empty_blob 0	symlink
+	EOF
+	attr_check_object_mode normal 100644 --cached &&
+	attr_check_object_mode exec 100755 --cached &&
+	attr_check_object_mode symlink 120000 --cached
+'
+
+test_expect_success 'check object mode attributes work for submodules' '
+	mkdir sub &&
+	(
+		cd sub &&
+		git init &&
+		mv .git .real &&
+		echo "gitdir: .real" >.git &&
+		test_commit first
+	) &&
+	attr_check_object_mode sub 160000 &&
+	attr_check_object_mode sub unspecified --cached &&
+	git add sub &&
+	attr_check_object_mode sub 160000 --cached
+'
+
+test_expect_success 'we do not allow user defined builtin_* attributes' '
+	echo "foo* builtin_foo" >.gitattributes &&
+	git add .gitattributes 2>actual &&
+	echo "builtin_foo is not a valid attribute name: .gitattributes:1" >expect &&
+	test_cmp expect actual
+'
+
+test_expect_success 'user defined builtin_objectmode values are ignored' '
+	echo "foo* builtin_objectmode=12345" >.gitattributes &&
+	git add .gitattributes &&
+	>foo_1 &&
+	attr_check_object_mode_basic foo_1 100644 &&
+	echo "builtin_objectmode is not a valid attribute name: .gitattributes:1" >expect &&
+	test_cmp expect err
+'
+
 test_done
diff --git a/t/t0009-prio-queue.sh b/t/t0009-prio-queue.sh
deleted file mode 100755
index eea9910..0000000
--- a/t/t0009-prio-queue.sh
+++ /dev/null
@@ -1,66 +0,0 @@
-#!/bin/sh
-
-test_description='basic tests for priority queue implementation'
-
-TEST_PASSES_SANITIZE_LEAK=true
-. ./test-lib.sh
-
-cat >expect <<'EOF'
-1
-2
-3
-4
-5
-5
-6
-7
-8
-9
-10
-EOF
-test_expect_success 'basic ordering' '
-	test-tool prio-queue 2 6 3 10 9 5 7 4 5 8 1 dump >actual &&
-	test_cmp expect actual
-'
-
-cat >expect <<'EOF'
-2
-3
-4
-1
-5
-6
-EOF
-test_expect_success 'mixed put and get' '
-	test-tool prio-queue 6 2 4 get 5 3 get get 1 dump >actual &&
-	test_cmp expect actual
-'
-
-cat >expect <<'EOF'
-1
-2
-NULL
-1
-2
-NULL
-EOF
-test_expect_success 'notice empty queue' '
-	test-tool prio-queue 1 2 get get get 1 2 get get get >actual &&
-	test_cmp expect actual
-'
-
-cat >expect <<'EOF'
-3
-2
-6
-4
-5
-1
-8
-EOF
-test_expect_success 'stack order' '
-	test-tool prio-queue stack 8 1 5 4 6 2 3 dump >actual &&
-	test_cmp expect actual
-'
-
-test_done
diff --git a/t/t0018-advice.sh b/t/t0018-advice.sh
index c13057a..0dcfb76 100755
--- a/t/t0018-advice.sh
+++ b/t/t0018-advice.sh
@@ -17,7 +17,6 @@
 test_expect_success 'advice should be printed when config variable is set to true' '
 	cat >expect <<-\EOF &&
 	hint: This is a piece of advice
-	hint: Disable this message with "git config advice.nestedTag false"
 	EOF
 	test_config advice.nestedTag true &&
 	test-tool advise "This is a piece of advice" 2>actual &&
diff --git a/t/t0024-crlf-archive.sh b/t/t0024-crlf-archive.sh
index a34de56..a7f4de4 100755
--- a/t/t0024-crlf-archive.sh
+++ b/t/t0024-crlf-archive.sh
@@ -9,7 +9,7 @@
 
 	git config core.autocrlf true &&
 
-	printf "CRLF line ending\r\nAnd another\r\n" > sample &&
+	printf "CRLF line ending\r\nAnd another\r\n" >sample &&
 	git add sample &&
 
 	test_tick &&
@@ -19,8 +19,9 @@
 
 test_expect_success 'tar archive' '
 
-	git archive --format=tar HEAD |
-	( mkdir untarred && cd untarred && "$TAR" -xf - ) &&
+	git archive --format=tar HEAD >test.tar &&
+	mkdir untarred &&
+	"$TAR" xf test.tar -C untarred &&
 
 	test_cmp sample untarred/sample
 
@@ -30,7 +31,11 @@
 
 	git archive --format=zip HEAD >test.zip &&
 
-	( mkdir unzipped && cd unzipped && "$GIT_UNZIP" ../test.zip ) &&
+	mkdir unzipped &&
+	(
+		cd unzipped &&
+		"$GIT_UNZIP" ../test.zip
+	) &&
 
 	test_cmp sample unzipped/sample
 
diff --git a/t/t0035-safe-bare-repository.sh b/t/t0035-safe-bare-repository.sh
index 038b8b7..8048856 100755
--- a/t/t0035-safe-bare-repository.sh
+++ b/t/t0035-safe-bare-repository.sh
@@ -78,4 +78,12 @@
 	expect_accepted_explicit "$pwd/outer-repo/bare-repo"
 '
 
+test_expect_success 'no trace when "bare repository" is .git' '
+	expect_accepted_implicit -C outer-repo/.git
+'
+
+test_expect_success 'no trace when "bare repository" is a subdir of .git' '
+	expect_accepted_implicit -C outer-repo/.git/objects
+'
+
 test_done
diff --git a/t/t0070-fundamental.sh b/t/t0070-fundamental.sh
index f18f928..0ecec2b 100755
--- a/t/t0070-fundamental.sh
+++ b/t/t0070-fundamental.sh
@@ -9,10 +9,6 @@
 TEST_PASSES_SANITIZE_LEAK=true
 . ./test-lib.sh
 
-test_expect_success 'character classes (isspace, isalpha etc.)' '
-	test-tool ctype
-'
-
 test_expect_success 'mktemp to nonexistent directory prints filename' '
 	test_must_fail test-tool mktemp doesnotexist/testXXXXXX 2>err &&
 	grep "doesnotexist/test" err
diff --git a/t/t0080-unit-test-output.sh b/t/t0080-unit-test-output.sh
new file mode 100755
index 0000000..6657c11
--- /dev/null
+++ b/t/t0080-unit-test-output.sh
@@ -0,0 +1,59 @@
+#!/bin/sh
+
+test_description='Test the output of the unit test framework'
+
+TEST_PASSES_SANITIZE_LEAK=true
+. ./test-lib.sh
+
+test_expect_success 'TAP output from unit tests' '
+	cat >expect <<-EOF &&
+	ok 1 - passing test
+	ok 2 - passing test and assertion return 1
+	# check "1 == 2" failed at t/unit-tests/t-basic.c:76
+	#    left: 1
+	#   right: 2
+	not ok 3 - failing test
+	ok 4 - failing test and assertion return 0
+	not ok 5 - passing TEST_TODO() # TODO
+	ok 6 - passing TEST_TODO() returns 1
+	# todo check ${SQ}check(x)${SQ} succeeded at t/unit-tests/t-basic.c:25
+	not ok 7 - failing TEST_TODO()
+	ok 8 - failing TEST_TODO() returns 0
+	# check "0" failed at t/unit-tests/t-basic.c:30
+	# skipping test - missing prerequisite
+	# skipping check ${SQ}1${SQ} at t/unit-tests/t-basic.c:32
+	ok 9 - test_skip() # SKIP
+	ok 10 - skipped test returns 1
+	# skipping test - missing prerequisite
+	ok 11 - test_skip() inside TEST_TODO() # SKIP
+	ok 12 - test_skip() inside TEST_TODO() returns 1
+	# check "0" failed at t/unit-tests/t-basic.c:48
+	not ok 13 - TEST_TODO() after failing check
+	ok 14 - TEST_TODO() after failing check returns 0
+	# check "0" failed at t/unit-tests/t-basic.c:56
+	not ok 15 - failing check after TEST_TODO()
+	ok 16 - failing check after TEST_TODO() returns 0
+	# check "!strcmp("\thello\\\\", "there\"\n")" failed at t/unit-tests/t-basic.c:61
+	#    left: "\011hello\\\\"
+	#   right: "there\"\012"
+	# check "!strcmp("NULL", NULL)" failed at t/unit-tests/t-basic.c:62
+	#    left: "NULL"
+	#   right: NULL
+	# check "${SQ}a${SQ} == ${SQ}\n${SQ}" failed at t/unit-tests/t-basic.c:63
+	#    left: ${SQ}a${SQ}
+	#   right: ${SQ}\012${SQ}
+	# check "${SQ}\\\\${SQ} == ${SQ}\\${SQ}${SQ}" failed at t/unit-tests/t-basic.c:64
+	#    left: ${SQ}\\\\${SQ}
+	#   right: ${SQ}\\${SQ}${SQ}
+	not ok 17 - messages from failing string and char comparison
+	# BUG: test has no checks at t/unit-tests/t-basic.c:91
+	not ok 18 - test with no checks
+	ok 19 - test with no checks returns 0
+	1..19
+	EOF
+
+	! "$GIT_BUILD_DIR"/t/unit-tests/bin/t-basic >actual &&
+	test_cmp expect actual
+'
+
+test_done
diff --git a/t/t0091-bugreport.sh b/t/t0091-bugreport.sh
index 8798fee..fca3904 100755
--- a/t/t0091-bugreport.sh
+++ b/t/t0091-bugreport.sh
@@ -39,9 +39,9 @@
 
 	sed -ne "/^\[System Info\]$/,/^$/p" <git-bugreport-format.txt >system &&
 
-	# The beginning should match "git version --build-info" verbatim,
+	# The beginning should match "git version --build-options" verbatim,
 	# but rather than checking bit-for-bit equality, just test some basics.
-	grep "git version [0-9]." system &&
+	grep "git version " system &&
 	grep "shell-path: ." system &&
 
 	# After the version, there should be some more info.
diff --git a/t/t0600-reffiles-backend.sh b/t/t0600-reffiles-backend.sh
new file mode 100755
index 0000000..e6a5f18
--- /dev/null
+++ b/t/t0600-reffiles-backend.sh
@@ -0,0 +1,384 @@
+#!/bin/sh
+
+test_description='Test reffiles backend'
+
+GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME=main
+export GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME
+
+TEST_PASSES_SANITIZE_LEAK=true
+. ./test-lib.sh
+
+if ! test_have_prereq REFFILES
+then
+	skip_all='skipping reffiles specific tests'
+	test_done
+fi
+
+test_expect_success 'setup' '
+	git commit --allow-empty -m Initial &&
+	C=$(git rev-parse HEAD) &&
+	git commit --allow-empty -m Second &&
+	D=$(git rev-parse HEAD) &&
+	git commit --allow-empty -m Third &&
+	E=$(git rev-parse HEAD)
+'
+
+test_expect_success 'empty directory should not fool rev-parse' '
+	prefix=refs/e-rev-parse &&
+	git update-ref $prefix/foo $C &&
+	git pack-refs --all &&
+	mkdir -p .git/$prefix/foo/bar/baz &&
+	echo "$C" >expected &&
+	git rev-parse $prefix/foo >actual &&
+	test_cmp expected actual
+'
+
+test_expect_success 'empty directory should not fool for-each-ref' '
+	prefix=refs/e-for-each-ref &&
+	git update-ref $prefix/foo $C &&
+	git for-each-ref $prefix >expected &&
+	git pack-refs --all &&
+	mkdir -p .git/$prefix/foo/bar/baz &&
+	git for-each-ref $prefix >actual &&
+	test_cmp expected actual
+'
+
+test_expect_success 'empty directory should not fool create' '
+	prefix=refs/e-create &&
+	mkdir -p .git/$prefix/foo/bar/baz &&
+	printf "create %s $C\n" $prefix/foo |
+	git update-ref --stdin
+'
+
+test_expect_success 'empty directory should not fool verify' '
+	prefix=refs/e-verify &&
+	git update-ref $prefix/foo $C &&
+	git pack-refs --all &&
+	mkdir -p .git/$prefix/foo/bar/baz &&
+	printf "verify %s $C\n" $prefix/foo |
+	git update-ref --stdin
+'
+
+test_expect_success 'empty directory should not fool 1-arg update' '
+	prefix=refs/e-update-1 &&
+	git update-ref $prefix/foo $C &&
+	git pack-refs --all &&
+	mkdir -p .git/$prefix/foo/bar/baz &&
+	printf "update %s $D\n" $prefix/foo |
+	git update-ref --stdin
+'
+
+test_expect_success 'empty directory should not fool 2-arg update' '
+	prefix=refs/e-update-2 &&
+	git update-ref $prefix/foo $C &&
+	git pack-refs --all &&
+	mkdir -p .git/$prefix/foo/bar/baz &&
+	printf "update %s $D $C\n" $prefix/foo |
+	git update-ref --stdin
+'
+
+test_expect_success 'empty directory should not fool 0-arg delete' '
+	prefix=refs/e-delete-0 &&
+	git update-ref $prefix/foo $C &&
+	git pack-refs --all &&
+	mkdir -p .git/$prefix/foo/bar/baz &&
+	printf "delete %s\n" $prefix/foo |
+	git update-ref --stdin
+'
+
+test_expect_success 'empty directory should not fool 1-arg delete' '
+	prefix=refs/e-delete-1 &&
+	git update-ref $prefix/foo $C &&
+	git pack-refs --all &&
+	mkdir -p .git/$prefix/foo/bar/baz &&
+	printf "delete %s $C\n" $prefix/foo |
+	git update-ref --stdin
+'
+
+test_expect_success 'non-empty directory blocks create' '
+	prefix=refs/ne-create &&
+	mkdir -p .git/$prefix/foo/bar &&
+	: >.git/$prefix/foo/bar/baz.lock &&
+	test_when_finished "rm -f .git/$prefix/foo/bar/baz.lock" &&
+	cat >expected <<-EOF &&
+	fatal: cannot lock ref $SQ$prefix/foo$SQ: there is a non-empty directory $SQ.git/$prefix/foo$SQ blocking reference $SQ$prefix/foo$SQ
+	EOF