git-commit-vandalism/t/t3430-rebase-merges.sh

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rebase: introduce the --rebase-merges option Once upon a time, this here developer thought: wouldn't it be nice if, say, Git for Windows' patches on top of core Git could be represented as a thicket of branches, and be rebased on top of core Git in order to maintain a cherry-pick'able set of patch series? The original attempt to answer this was: git rebase --preserve-merges. However, that experiment was never intended as an interactive option, and it only piggy-backed on git rebase --interactive because that command's implementation looked already very, very familiar: it was designed by the same person who designed --preserve-merges: yours truly. Some time later, some other developer (I am looking at you, Andreas! ;-)) decided that it would be a good idea to allow --preserve-merges to be combined with --interactive (with caveats!) and the Git maintainer (well, the interim Git maintainer during Junio's absence, that is) agreed, and that is when the glamor of the --preserve-merges design started to fall apart rather quickly and unglamorously. The reason? In --preserve-merges mode, the parents of a merge commit (or for that matter, of *any* commit) were not stated explicitly, but were *implied* by the commit name passed to the `pick` command. This made it impossible, for example, to reorder commits. Not to mention to move commits between branches or, deity forbid, to split topic branches into two. Alas, these shortcomings also prevented that mode (whose original purpose was to serve Git for Windows' needs, with the additional hope that it may be useful to others, too) from serving Git for Windows' needs. Five years later, when it became really untenable to have one unwieldy, big hodge-podge patch series of partly related, partly unrelated patches in Git for Windows that was rebased onto core Git's tags from time to time (earning the undeserved wrath of the developer of the ill-fated git-remote-hg series that first obsoleted Git for Windows' competing approach, only to be abandoned without maintainer later) was really untenable, the "Git garden shears" were born [*1*/*2*]: a script, piggy-backing on top of the interactive rebase, that would first determine the branch topology of the patches to be rebased, create a pseudo todo list for further editing, transform the result into a real todo list (making heavy use of the `exec` command to "implement" the missing todo list commands) and finally recreate the patch series on top of the new base commit. That was in 2013. And it took about three weeks to come up with the design and implement it as an out-of-tree script. Needless to say, the implementation needed quite a few years to stabilize, all the while the design itself proved itself sound. With this patch, the goodness of the Git garden shears comes to `git rebase -i` itself. Passing the `--rebase-merges` option will generate a todo list that can be understood readily, and where it is obvious how to reorder commits. New branches can be introduced by inserting `label` commands and calling `merge <label>`. And once this mode will have become stable and universally accepted, we can deprecate the design mistake that was `--preserve-merges`. Link *1*: https://github.com/msysgit/msysgit/blob/master/share/msysGit/shears.sh Link *2*: https://github.com/git-for-windows/build-extra/blob/master/shears.sh Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2018-04-25 14:29:04 +02:00
#!/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
'
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>
2018-04-25 14:29:40 +02:00
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
'
rebase: introduce the --rebase-merges option Once upon a time, this here developer thought: wouldn't it be nice if, say, Git for Windows' patches on top of core Git could be represented as a thicket of branches, and be rebased on top of core Git in order to maintain a cherry-pick'able set of patch series? The original attempt to answer this was: git rebase --preserve-merges. However, that experiment was never intended as an interactive option, and it only piggy-backed on git rebase --interactive because that command's implementation looked already very, very familiar: it was designed by the same person who designed --preserve-merges: yours truly. Some time later, some other developer (I am looking at you, Andreas! ;-)) decided that it would be a good idea to allow --preserve-merges to be combined with --interactive (with caveats!) and the Git maintainer (well, the interim Git maintainer during Junio's absence, that is) agreed, and that is when the glamor of the --preserve-merges design started to fall apart rather quickly and unglamorously. The reason? In --preserve-merges mode, the parents of a merge commit (or for that matter, of *any* commit) were not stated explicitly, but were *implied* by the commit name passed to the `pick` command. This made it impossible, for example, to reorder commits. Not to mention to move commits between branches or, deity forbid, to split topic branches into two. Alas, these shortcomings also prevented that mode (whose original purpose was to serve Git for Windows' needs, with the additional hope that it may be useful to others, too) from serving Git for Windows' needs. Five years later, when it became really untenable to have one unwieldy, big hodge-podge patch series of partly related, partly unrelated patches in Git for Windows that was rebased onto core Git's tags from time to time (earning the undeserved wrath of the developer of the ill-fated git-remote-hg series that first obsoleted Git for Windows' competing approach, only to be abandoned without maintainer later) was really untenable, the "Git garden shears" were born [*1*/*2*]: a script, piggy-backing on top of the interactive rebase, that would first determine the branch topology of the patches to be rebased, create a pseudo todo list for further editing, transform the result into a real todo list (making heavy use of the `exec` command to "implement" the missing todo list commands) and finally recreate the patch series on top of the new base commit. That was in 2013. And it took about three weeks to come up with the design and implement it as an out-of-tree script. Needless to say, the implementation needed quite a few years to stabilize, all the while the design itself proved itself sound. With this patch, the goodness of the Git garden shears comes to `git rebase -i` itself. Passing the `--rebase-merges` option will generate a todo list that can be understood readily, and where it is obvious how to reorder commits. New branches can be introduced by inserting `label` commands and calling `merge <label>`. And once this mode will have become stable and universally accepted, we can deprecate the design mistake that was `--preserve-merges`. Link *1*: https://github.com/msysgit/msysgit/blob/master/share/msysGit/shears.sh Link *2*: https://github.com/git-for-windows/build-extra/blob/master/shears.sh Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2018-04-25 14:29:04 +02:00
test_done