RelNotes - jrn/git - Git at Google

 Git Release Notes
 =================

 Backward Compatibility Notes
 ----------------------------

  * "git branch -l <foo>" used to be a way to ask a reflog to be
    created while creating a new branch, but that is no longer the
    case.  It is a short-hand for "git branch --list <foo>" now.

  * "git push" into refs/tags/* hierarchy is rejected without getting
    forced, but "git fetch" (misguidedly) used the "fast forwarding"
    rule used for the refs/heads/* hierarchy; this has been corrected,
    which means some fetches of tags that did not fail with older
    version of Git will fail without "--force" with this version.


 Updates since v2.19
 -------------------

 UI, Workflows & Features

  * Running "git clone" against a project that contain two files with
    pathnames that differ only in cases on a case insensitive
    filesystem would result in one of the files lost because the
    underlying filesystem is incapable of holding both at the same
    time.  An attempt is made to detect such a case and warn.

  * "git checkout -b newbranch [HEAD]" should not have to do as much as
    checking out a commit different from HEAD.  An attempt is made to
    optimize this special case.

  * "git rev-list --stdin </dev/null" used to be an error; it now shows
    no output without an error.  "git rev-list --stdin --default HEAD"
    still falls back to the given default when nothing is given on the
    standard input.

  * Lift code from GitHub to restrict delta computation so that an
    object that exists in one fork is not made into a delta against
    another object that does not appear in the same forked repository.

  * "git format-patch" learned new "--interdiff" and "--range-diff"
    options to explain the difference between this version and the
    previous attempt in the cover letter (or after the tree-dashes as
    a comment).

  * "git mailinfo" used in "git am" learned to make a best-effort
    recovery of a patch corrupted by MUA that sends text/plain with
    format=flawed option.
    (merge 3aa4d81f88 rs/mailinfo-format-flowed later to maint).

  * The rules used by "git push" and "git fetch" to determine if a ref
    can or cannot be updated were inconsistent; specifically, fetching
    to update existing tags were allowed even though tags are supposed
    to be unmoving anchoring points.  "git fetch" was taught to forbid
    updates to existing tags without the "--force" option.


 Performance, Internal Implementation, Development Support etc.

  * When there are too many packfiles in a repository (which is not
    recommended), looking up an object in these would require
    consulting many pack .idx files; a new mechanism to have a single
    file that consolidates all of these .idx files is introduced.

  * "git submodule update" is getting rewritten piece-by-piece into C.

  * The code for computing history reachability has been shuffled,
    obtained a bunch of new tests to cover them, and then being
    improved.

  * The unpack_trees() API used in checking out a branch and merging
    walks one or more trees along with the index.  When the cache-tree
    in the index tells us that we are walking a tree whose flattened
    contents is known (i.e. matches a span in the index), as linearly
    scanning a span in the index is much more efficient than having to
    open tree objects recursively and listing their entries, the walk
    can be optimized, which has been done.

  * When creating a thin pack, which allows objects to be made into a
    delta against another object that is not in the resulting pack but
    is known to be present on the receiving end, the code learned to
    take advantage of the reachability bitmap; this allows the server
    to send a delta against a base beyond the "boundary" commit.

  * spatch transformation to replace boolean uses of !hashcmp() to
    newly introduced oideq() is added, and applied, to regain
    performance lost due to support of multiple hash algorithms.

  * Fix a bug in which the same path could be registered under multiple
    worktree entries if the path was missing (for instance, was removed
    manually).  Also, as a convenience, expand the number of cases in
    which --force is applicable.


 Fixes since v2.19
 -----------------

  * "git interpret-trailers" and its underlying machinery had a buggy
    code that attempted to ignore patch text after commit log message,
    which triggered in various codepaths that will always get the log
    message alone and never get such an input.
    (merge 66e83d9b41 jk/trailer-fixes later to maint).

  * Malformed or crafted data in packstream can make our code attempt
    to read or write past the allocated buffer and abort, instead of
    reporting an error, which has been fixed.

  * Code cleanup, docfix, build fix, etc.
    (merge 96a7501aad ts/doc-build-manpage-xsl-quietly later to maint).
    (merge b9b07efdb2 tg/conflict-marker-size later to maint).
    (merge fa0aeea770 sg/doc-trace-appends later to maint).
	Git Release Notes
	=================

	Backward Compatibility Notes
	----------------------------

	* "git branch -l <foo>" used to be a way to ask a reflog to be
	created while creating a new branch, but that is no longer the
	case. It is a short-hand for "git branch --list <foo>" now.

	* "git push" into refs/tags/* hierarchy is rejected without getting
	forced, but "git fetch" (misguidedly) used the "fast forwarding"
	rule used for the refs/heads/* hierarchy; this has been corrected,
	which means some fetches of tags that did not fail with older
	version of Git will fail without "--force" with this version.


	Updates since v2.19
	-------------------

	UI, Workflows & Features

	* Running "git clone" against a project that contain two files with
	pathnames that differ only in cases on a case insensitive
	filesystem would result in one of the files lost because the
	underlying filesystem is incapable of holding both at the same
	time. An attempt is made to detect such a case and warn.

	* "git checkout -b newbranch [HEAD]" should not have to do as much as
	checking out a commit different from HEAD. An attempt is made to
	optimize this special case.

	* "git rev-list --stdin </dev/null" used to be an error; it now shows
	no output without an error. "git rev-list --stdin --default HEAD"
	still falls back to the given default when nothing is given on the
	standard input.

	* Lift code from GitHub to restrict delta computation so that an
	object that exists in one fork is not made into a delta against
	another object that does not appear in the same forked repository.

	* "git format-patch" learned new "--interdiff" and "--range-diff"
	options to explain the difference between this version and the
	previous attempt in the cover letter (or after the tree-dashes as
	a comment).

	* "git mailinfo" used in "git am" learned to make a best-effort
	recovery of a patch corrupted by MUA that sends text/plain with
	format=flawed option.
	(merge 3aa4d81f88 rs/mailinfo-format-flowed later to maint).

	* The rules used by "git push" and "git fetch" to determine if a ref
	can or cannot be updated were inconsistent; specifically, fetching
	to update existing tags were allowed even though tags are supposed
	to be unmoving anchoring points. "git fetch" was taught to forbid
	updates to existing tags without the "--force" option.


	Performance, Internal Implementation, Development Support etc.

	* When there are too many packfiles in a repository (which is not
	recommended), looking up an object in these would require
	consulting many pack .idx files; a new mechanism to have a single
	file that consolidates all of these .idx files is introduced.

	* "git submodule update" is getting rewritten piece-by-piece into C.

	* The code for computing history reachability has been shuffled,
	obtained a bunch of new tests to cover them, and then being
	improved.

	* The unpack_trees() API used in checking out a branch and merging
	walks one or more trees along with the index. When the cache-tree
	in the index tells us that we are walking a tree whose flattened
	contents is known (i.e. matches a span in the index), as linearly
	scanning a span in the index is much more efficient than having to
	open tree objects recursively and listing their entries, the walk
	can be optimized, which has been done.

	* When creating a thin pack, which allows objects to be made into a
	delta against another object that is not in the resulting pack but
	is known to be present on the receiving end, the code learned to
	take advantage of the reachability bitmap; this allows the server
	to send a delta against a base beyond the "boundary" commit.

	* spatch transformation to replace boolean uses of !hashcmp() to
	newly introduced oideq() is added, and applied, to regain
	performance lost due to support of multiple hash algorithms.

	* Fix a bug in which the same path could be registered under multiple
	worktree entries if the path was missing (for instance, was removed
	manually). Also, as a convenience, expand the number of cases in
	which --force is applicable.


	Fixes since v2.19
	-----------------

	* "git interpret-trailers" and its underlying machinery had a buggy
	code that attempted to ignore patch text after commit log message,
	which triggered in various codepaths that will always get the log
	message alone and never get such an input.
	(merge 66e83d9b41 jk/trailer-fixes later to maint).

	* Malformed or crafted data in packstream can make our code attempt
	to read or write past the allocated buffer and abort, instead of
	reporting an error, which has been fixed.

	* Code cleanup, docfix, build fix, etc.
	(merge 96a7501aad ts/doc-build-manpage-xsl-quietly later to maint).
	(merge b9b07efdb2 tg/conflict-marker-size later to maint).
	(merge fa0aeea770 sg/doc-trace-appends later to maint).