rebase -i: introduce --rebase-merges=[no-]rebase-cousins
When running `git rebase --rebase-merges` non-interactively with an
ancestor of HEAD as <upstream> (or leaving the todo list unmodified),
we would ideally recreate the exact same commits as before the rebase.
However, if there are commits in the commit range <upstream>.. that do not
have <upstream> as direct ancestor (i.e. if `git log <upstream>..` would
show commits that are omitted by `git log --ancestry-path <upstream>..`),
this is currently not the case: we would turn them into commits that have
<upstream> as direct ancestor.
Let's illustrate that with a diagram:
C
/ \
A - B - E - F
\ /
D
Currently, after running `git rebase -i --rebase-merges B`, the new branch
structure would be (pay particular attention to the commit `D`):
--- C' --
/ \
A - B ------ E' - F'
\ /
D'
This is not really preserving the branch topology from before! The
reason is that the commit `D` does not have `B` as ancestor, and
therefore it gets rebased onto `B`.
This is unintuitive behavior. Even worse, when recreating branch
structure, most use cases would appear to want cousins *not* to be
rebased onto the new base commit. For example, Git for Windows (the
heaviest user of the Git garden shears, which served as the blueprint
for --rebase-merges) frequently merges branches from `next` early, and
these branches certainly do *not* want to be rebased. In the example
above, the desired outcome would look like this:
--- C' --
/ \
A - B ------ E' - F'
\ /
-- D' --
Let's introduce the term "cousins" for such commits ("D" in the
example), and let's not rebase them by default. For hypothetical
use cases where cousins *do* need to be rebased, `git rebase
--rebase=merges=rebase-cousins` needs to be used.
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/git-rebase.sh b/git-rebase.sh
index a553f96..40be59e 100755
--- a/git-rebase.sh
+++ b/git-rebase.sh
@@ -17,7 +17,7 @@
autostash automatically stash/stash pop before and after
fork-point use 'merge-base --fork-point' to refine upstream
onto=! rebase onto given branch instead of upstream
-r,rebase-merges! try to rebase merges instead of skipping them
+r,rebase-merges? try to rebase merges instead of skipping them
p,preserve-merges! try to recreate merges instead of ignoring them
s,strategy=! use the given merge strategy
no-ff! cherry-pick all commits, even if unchanged
@@ -91,6 +91,7 @@
# One of {'', continue, skip, abort}, as parsed from command line
action=
rebase_merges=
+rebase_cousins=
preserve_merges=
autosquash=
keep_empty=
@@ -286,6 +287,15 @@
rebase_merges=t
test -z "$interactive_rebase" && interactive_rebase=implied
;;
+ --rebase-merges=*)
+ rebase_merges=t
+ case "${1#*=}" in
+ rebase-cousins) rebase_cousins=t;;
+ no-rebase-cousins) rebase_cousins=;;
+ *) die "Unknown mode: $1";;
+ esac
+ test -z "$interactive_rebase" && interactive_rebase=implied
+ ;;
--preserve-merges)
preserve_merges=t
test -z "$interactive_rebase" && interactive_rebase=implied
