git-commit-vandalism/t/t3430-rebase-merges.sh
Johannes Schindelin 7543f6f444 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>
2018-04-26 12:28:43 +09:00

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#!/bin/sh
#
# Copyright (c) 2018 Johannes E. Schindelin
#
test_description='git rebase -i --rebase-merges
This test runs git rebase "interactively", retaining the branch structure by
recreating merge commits.
Initial setup:
-- B -- (first)
/ \
A - C - D - E - H (master)
\ /
F - G (second)
'
. ./test-lib.sh
. "$TEST_DIRECTORY"/lib-rebase.sh
test_cmp_graph () {
cat >expect &&
git log --graph --boundary --format=%s "$@" >output &&
sed "s/ *$//" <output >output.trimmed &&
test_cmp expect output.trimmed
}
test_expect_success 'setup' '
write_script replace-editor.sh <<-\EOF &&
mv "$1" "$(git rev-parse --git-path ORIGINAL-TODO)"
cp script-from-scratch "$1"
EOF
test_commit A &&
git checkout -b first &&
test_commit B &&
git checkout master &&
test_commit C &&
test_commit D &&
git merge --no-commit B &&
test_tick &&
git commit -m E &&
git tag -m E E &&
git checkout -b second C &&
test_commit F &&
test_commit G &&
git checkout master &&
git merge --no-commit G &&
test_tick &&
git commit -m H &&
git tag -m H H
'
test_expect_success 'create completely different structure' '
cat >script-from-scratch <<-\EOF &&
label onto
# onebranch
pick G
pick D
label onebranch
# second
reset onto
pick B
label second
reset onto
merge -C H second
merge onebranch # Merge the topic branch '\''onebranch'\''
EOF
test_config sequence.editor \""$PWD"/replace-editor.sh\" &&
test_tick &&
git rebase -i -r A &&
test_cmp_graph <<-\EOF
* Merge the topic branch '\''onebranch'\''
|\
| * D
| * G
* | H
|\ \
| |/
|/|
| * B
|/
* A
EOF
'
test_expect_success 'generate correct todo list' '
cat >expect <<-\EOF &&
label onto
reset onto
pick d9df450 B
label E
reset onto
pick 5dee784 C
label branch-point
pick ca2c861 F
pick 088b00a G
label H
reset branch-point # C
pick 12bd07b D
merge -C 2051b56 E # E
merge -C 233d48a H # H
EOF
grep -v "^#" <.git/ORIGINAL-TODO >output &&
test_cmp expect output
'
test_expect_success '`reset` refuses to overwrite untracked files' '
git checkout -b refuse-to-reset &&
test_commit dont-overwrite-untracked &&
git checkout @{-1} &&
: >dont-overwrite-untracked.t &&
echo "reset refs/tags/dont-overwrite-untracked" >script-from-scratch &&
test_config sequence.editor \""$PWD"/replace-editor.sh\" &&
test_must_fail git rebase -r HEAD &&
git rebase --abort
'
test_expect_success 'failed `merge` writes patch (may be rescheduled, too)' '
test_when_finished "test_might_fail git rebase --abort" &&
git checkout -b conflicting-merge A &&
: fail because of conflicting untracked file &&
>G.t &&
echo "merge -C H G" >script-from-scratch &&
test_config sequence.editor \""$PWD"/replace-editor.sh\" &&
test_tick &&
test_must_fail git rebase -ir HEAD &&
grep "^merge -C .* G$" .git/rebase-merge/done &&
grep "^merge -C .* G$" .git/rebase-merge/git-rebase-todo &&
test_path_is_file .git/rebase-merge/patch &&
: fail because of merge conflict &&
rm G.t .git/rebase-merge/patch &&
git reset --hard &&
test_commit conflicting-G G.t not-G conflicting-G &&
test_must_fail git rebase --continue &&
! grep "^merge -C .* G$" .git/rebase-merge/git-rebase-todo &&
test_path_is_file .git/rebase-merge/patch
'
test_expect_success 'with a branch tip that was cherry-picked already' '
git checkout -b already-upstream master &&
base="$(git rev-parse --verify HEAD)" &&
test_commit A1 &&
test_commit A2 &&
git reset --hard $base &&
test_commit B1 &&
test_tick &&
git merge -m "Merge branch A" A2 &&
git checkout -b upstream-with-a2 $base &&
test_tick &&
git cherry-pick A2 &&
git checkout already-upstream &&
test_tick &&
git rebase -i -r upstream-with-a2 &&
test_cmp_graph upstream-with-a2.. <<-\EOF
* Merge branch A
|\
| * A1
* | B1
|/
o A2
EOF
'
test_expect_success 'do not rebase cousins unless asked for' '
git checkout -b cousins master &&
before="$(git rev-parse --verify HEAD)" &&
test_tick &&
git rebase -r HEAD^ &&
test_cmp_rev HEAD $before &&
test_tick &&
git rebase --rebase-merges=rebase-cousins HEAD^ &&
test_cmp_graph HEAD^.. <<-\EOF
* Merge the topic branch '\''onebranch'\''
|\
| * D
| * G
|/
o H
EOF
'
test_expect_success 'refs/rewritten/* is worktree-local' '
git worktree add wt &&
cat >wt/script-from-scratch <<-\EOF &&
label xyz
exec GIT_DIR=../.git git rev-parse --verify refs/rewritten/xyz >a || :
exec git rev-parse --verify refs/rewritten/xyz >b
EOF
test_config -C wt sequence.editor \""$PWD"/replace-editor.sh\" &&
git -C wt rebase -i HEAD &&
test_must_be_empty wt/a &&
test_cmp_rev HEAD "$(cat wt/b)"
'
test_expect_success 'post-rewrite hook and fixups work for merges' '
git checkout -b post-rewrite &&
test_commit same1 &&
git reset --hard HEAD^ &&
test_commit same2 &&
git merge -m "to fix up" same1 &&
echo same old same old >same2.t &&
test_tick &&
git commit --fixup HEAD same2.t &&
fixup="$(git rev-parse HEAD)" &&
mkdir -p .git/hooks &&
test_when_finished "rm .git/hooks/post-rewrite" &&
echo "cat >actual" | write_script .git/hooks/post-rewrite &&
test_tick &&
git rebase -i --autosquash -r HEAD^^^ &&
printf "%s %s\n%s %s\n%s %s\n%s %s\n" >expect $(git rev-parse \
$fixup^^2 HEAD^2 \
$fixup^^ HEAD^ \
$fixup^ HEAD \
$fixup HEAD) &&
test_cmp expect actual
'
test_expect_success 'refuse to merge ancestors of HEAD' '
echo "merge HEAD^" >script-from-scratch &&
test_config -C wt sequence.editor \""$PWD"/replace-editor.sh\" &&
before="$(git rev-parse HEAD)" &&
git rebase -i HEAD &&
test_cmp_rev HEAD $before
'
test_done