@matheusbsbs / matheus-bagliano / commits / 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>

Johannes Schindelin committed Apr 25, 2018 at 14:29 UTC 7543f6f4441a0ec76460a54f90ab8674fe424786

7 files changed +59 -6

Documentation/git-rebase.txt

+11 -4

@@ -380,7 +380,7 @@ rebase.instructionFormat. A customized instruction format will automatically

380 have the long commit hash prepended to the format.

381

382 -r::

383 ---rebase-merges::

383 +--rebase-merges[=(rebase-cousins|no-rebase-cousins)]::

384 By default, a rebase will simply drop merge commits from the todo

385 list, and put the rebased commits into a single, linear branch.

386 With `--rebase-merges`, the rebase will instead try to preserve

@@ -389,9 +389,16 @@ have the long commit hash prepended to the format.

389 manual amendments in these merge commits will have to be

390 resolved/re-applied manually.

391 +

392 -This mode is similar in spirit to `--preserve-merges`, but in contrast to

393 -that option works well in interactive rebases: commits can be reordered,

394 -inserted and dropped at will.

392 +By default, or when `no-rebase-cousins` was specified, commits which do not

393 +have `<upstream>` as direct ancestor will keep their original branch point,

394 +i.e. commits that would be excluded by gitlink:git-log[1]'s

395 +`--ancestry-path` option will keep their original ancestry by default. If

396 +the `rebase-cousins` mode is turned on, such commits are instead rebased

397 +onto `<upstream>` (or `<onto>`, if specified).

398 ++

399 +The `--rebase-merges` mode is similar in spirit to `--preserve-merges`, but

400 +in contrast to that option works well in interactive rebases: commits can be

401 +reordered, inserted and dropped at will.

402 +

403 It is currently only possible to recreate the merge commits using the

404 `recursive` merge strategy; Different merge strategies can be used only via

builtin/rebase--helper.c

+8 -1

@@ -13,7 +13,7 @@ int cmd_rebase__helper(int argc, const char **argv, const char *prefix)

13 {

14 struct replay_opts opts = REPLAY_OPTS_INIT;

15 unsigned flags = 0, keep_empty = 0, rebase_merges = 0;

16 - int abbreviate_commands = 0;

16 + int abbreviate_commands = 0, rebase_cousins = -1;

17 enum {

18 CONTINUE = 1, ABORT, MAKE_SCRIPT, SHORTEN_OIDS, EXPAND_OIDS,

19 CHECK_TODO_LIST, SKIP_UNNECESSARY_PICKS, REARRANGE_SQUASH,

@@ -25,6 +25,8 @@ int cmd_rebase__helper(int argc, const char **argv, const char *prefix)

25 OPT_BOOL(0, "allow-empty-message", &opts.allow_empty_message,

26 N_("allow commits with empty messages")),

27 OPT_BOOL(0, "rebase-merges", &rebase_merges, N_("rebase merge commits")),

28 + OPT_BOOL(0, "rebase-cousins", &rebase_cousins,

29 + N_("keep original branch points of cousins")),

30 OPT_CMDMODE(0, "continue", &command, N_("continue rebase"),

31 CONTINUE),

32 OPT_CMDMODE(0, "abort", &command, N_("abort rebase"),

@@ -59,8 +61,13 @@ int cmd_rebase__helper(int argc, const char **argv, const char *prefix)

61 flags |= keep_empty ? TODO_LIST_KEEP_EMPTY : 0;

62 flags |= abbreviate_commands ? TODO_LIST_ABBREVIATE_CMDS : 0;

63 flags |= rebase_merges ? TODO_LIST_REBASE_MERGES : 0;

64 + flags |= rebase_cousins > 0 ? TODO_LIST_REBASE_COUSINS : 0;

65 flags |= command == SHORTEN_OIDS ? TODO_LIST_SHORTEN_IDS : 0;

67 + if (rebase_cousins >= 0 && !rebase_merges)

68 + warning(_("--[no-]rebase-cousins has no effect without "

69 + "--rebase-merges"));

70 +

71 if (command == CONTINUE && argc == 1)

72 return !!sequencer_continue(&opts);

73 if (command == ABORT && argc == 1)

git-rebase--interactive.sh

@@ -971,6 +971,7 @@ git_rebase__interactive () {

971

972 git rebase--helper --make-script ${keep_empty:+--keep-empty} \

973 ${rebase_merges:+--rebase-merges} \

974 + ${rebase_cousins:+--rebase-cousins} \

975 $revisions ${restrict_revision+^$restrict_revision} >"$todo" ||

976 die "$(gettext "Could not generate todo list")"

977

git-rebase.sh

+11 -1

@@ -17,7 +17,7 @@ q,quiet! be quiet. implies --no-stat

17 autostash automatically stash/stash pop before and after

18 fork-point use 'merge-base --fork-point' to refine upstream

19 onto=! rebase onto given branch instead of upstream

20 -r,rebase-merges! try to rebase merges instead of skipping them

20 +r,rebase-merges? try to rebase merges instead of skipping them

21 p,preserve-merges! try to recreate merges instead of ignoring them

22 s,strategy=! use the given merge strategy

23 no-ff! cherry-pick all commits, even if unchanged

@@ -91,6 +91,7 @@ state_dir=

91 # One of {'', continue, skip, abort}, as parsed from command line

92 action=

93 rebase_merges=

94 +rebase_cousins=

95 preserve_merges=

96 autosquash=

97 keep_empty=

@@ -286,6 +287,15 @@ do

287 rebase_merges=t

288 test -z "$interactive_rebase" && interactive_rebase=implied

289 ;;

290 + --rebase-merges=*)

291 + rebase_merges=t

292 + case "${1#*=}" in

293 + rebase-cousins) rebase_cousins=t;;

294 + no-rebase-cousins) rebase_cousins=;;

295 + *) die "Unknown mode: $1";;

296 + esac

297 + test -z "$interactive_rebase" && interactive_rebase=implied

298 + ;;

299 --preserve-merges)

300 preserve_merges=t

301 test -z "$interactive_rebase" && interactive_rebase=implied

sequencer.c

@@ -3578,6 +3578,7 @@ static int make_script_with_merges(struct pretty_print_context *pp,

3578 unsigned flags)

3579 {

3580 int keep_empty = flags & TODO_LIST_KEEP_EMPTY;

3581 + int rebase_cousins = flags & TODO_LIST_REBASE_COUSINS;

3582 struct strbuf buf = STRBUF_INIT, oneline = STRBUF_INIT;

3583 struct strbuf label = STRBUF_INIT;

3584 struct commit_list *commits = NULL, **tail = &commits, *iter;

@@ -3755,6 +3756,9 @@ static int make_script_with_merges(struct pretty_print_context *pp,

3756 &commit->object.oid);

3757 if (entry)

3758 to = entry->string;

3759 + else if (!rebase_cousins)

3760 + to = label_oid(&commit->object.oid, NULL,

3761 + &state);

3762

3763 if (!to || !strcmp(to, "onto"))

3764 fprintf(out, "%s onto\n", cmd_reset);

sequencer.h

@@ -60,6 +60,12 @@ int sequencer_remove_state(struct replay_opts *opts);

60 #define TODO_LIST_SHORTEN_IDS (1U << 1)

61 #define TODO_LIST_ABBREVIATE_CMDS (1U << 2)

62 #define TODO_LIST_REBASE_MERGES (1U << 3)

63 +/*

64 + * When rebasing merges, commits that do have the base commit as ancestor

65 + * ("cousins") are *not* rebased onto the new base by default. If those

66 + * commits should be rebased onto the new base, this flag needs to be passed.

67 + */

68 +#define TODO_LIST_REBASE_COUSINS (1U << 4)

69 int sequencer_make_script(FILE *out, int argc, const char **argv,

70 unsigned flags);

t/t3430-rebase-merges.sh

+18

@@ -176,6 +176,24 @@ test_expect_success 'with a branch tip that was cherry-picked already' '

176 EOF

177 '

178

179 +test_expect_success 'do not rebase cousins unless asked for' '

180 + git checkout -b cousins master &&

181 + before="$(git rev-parse --verify HEAD)" &&

182 + test_tick &&

183 + git rebase -r HEAD^ &&

184 + test_cmp_rev HEAD $before &&

185 + test_tick &&

186 + git rebase --rebase-merges=rebase-cousins HEAD^ &&

187 + test_cmp_graph HEAD^.. <<-\EOF

188 + * Merge the topic branch '\''onebranch'\''

189 + |\

190 + | * D

191 + | * G

192 + |/

193 + o H

194 + EOF

195 +'

196 +

197 test_expect_success 'refs/rewritten/* is worktree-local' '

198 git worktree add wt &&

199 cat >wt/script-from-scratch <<-\EOF &&