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@xxxxxx>
---
Documentation/git-rebase.txt | 15 +++++++++++----
builtin/rebase--helper.c | 9 ++++++++-
git-rebase--interactive.sh | 1 +
git-rebase.sh | 12 +++++++++++-
sequencer.c | 4 ++++
sequencer.h | 6 ++++++
t/t3430-rebase-merges.sh | 18 ++++++++++++++++++
7 files changed, 59 insertions(+), 6 deletions(-)
diff --git a/Documentation/git-rebase.txt b/Documentation/git-rebase.txt
index 7f1756f1eba..fe681d69281 100644
--- a/Documentation/git-rebase.txt
+++ b/Documentation/git-rebase.txt
@@ -380,7 +380,7 @@ rebase.instructionFormat. A customized instruction format will automatically
have the long commit hash prepended to the format.
-r::
---rebase-merges::
+--rebase-merges[=(rebase-cousins|no-rebase-cousins)]::
By default, a rebase will simply drop merge commits from the todo
list, and put the rebased commits into a single, linear branch.
With `--rebase-merges`, the rebase will instead try to preserve
@@ -389,9 +389,16 @@ have the long commit hash prepended to the format.
manual amendments in these merge commits will have to be
resolved/re-applied manually.
+
-This mode is similar in spirit to `--preserve-merges`, but in contrast to
-that option works well in interactive rebases: commits can be reordered,
-inserted and dropped at will.
+By default, or when `no-rebase-cousins` was specified, commits which do not
+have `<upstream>` as direct ancestor will keep their original branch point,
+i.e. commits that would be excluded by gitlink:git-log[1]'s
+`--ancestry-path` option will keep their original ancestry by default. If
+the `rebase-cousins` mode is turned on, such commits are instead rebased
+onto `<upstream>` (or `<onto>`, if specified).
++
+The `--rebase-merges` mode is similar in spirit to `--preserve-merges`, but
+in contrast to that option works well in interactive rebases: commits can be
+reordered, inserted and dropped at will.
+
It is currently only possible to recreate the merge commits using the
`recursive` merge strategy; Different merge strategies can be used only via
diff --git a/builtin/rebase--helper.c b/builtin/rebase--helper.c
index 781782e7272..f7c2a5fdc81 100644
--- a/builtin/rebase--helper.c
+++ b/builtin/rebase--helper.c
@@ -13,7 +13,7 @@ int cmd_rebase__helper(int argc, const char **argv, const char *prefix)
{
struct replay_opts opts = REPLAY_OPTS_INIT;
unsigned flags = 0, keep_empty = 0, rebase_merges = 0;
- int abbreviate_commands = 0;
+ int abbreviate_commands = 0, rebase_cousins = -1;
enum {
CONTINUE = 1, ABORT, MAKE_SCRIPT, SHORTEN_OIDS, EXPAND_OIDS,
CHECK_TODO_LIST, SKIP_UNNECESSARY_PICKS, REARRANGE_SQUASH,
@@ -25,6 +25,8 @@ int cmd_rebase__helper(int argc, const char **argv, const char *prefix)
OPT_BOOL(0, "allow-empty-message", &opts.allow_empty_message,
N_("allow commits with empty messages")),
OPT_BOOL(0, "rebase-merges", &rebase_merges, N_("rebase merge commits")),
+ OPT_BOOL(0, "rebase-cousins", &rebase_cousins,
+ N_("keep original branch points of cousins")),
OPT_CMDMODE(0, "continue", &command, N_("continue rebase"),
CONTINUE),
OPT_CMDMODE(0, "abort", &command, N_("abort rebase"),
@@ -59,8 +61,13 @@ int cmd_rebase__helper(int argc, const char **argv, const char *prefix)
flags |= keep_empty ? TODO_LIST_KEEP_EMPTY : 0;
flags |= abbreviate_commands ? TODO_LIST_ABBREVIATE_CMDS : 0;
flags |= rebase_merges ? TODO_LIST_REBASE_MERGES : 0;
+ flags |= rebase_cousins > 0 ? TODO_LIST_REBASE_COUSINS : 0;
flags |= command == SHORTEN_OIDS ? TODO_LIST_SHORTEN_IDS : 0;
+ if (rebase_cousins >= 0 && !rebase_merges)
+ warning(_("--[no-]rebase-cousins has no effect without "
+ "--rebase-merges"));
+
if (command == CONTINUE && argc == 1)
return !!sequencer_continue(&opts);
if (command == ABORT && argc == 1)
diff --git a/git-rebase--interactive.sh b/git-rebase--interactive.sh
index e29da634339..cbf44f86482 100644
--- a/git-rebase--interactive.sh
+++ b/git-rebase--interactive.sh
@@ -971,6 +971,7 @@ git_rebase__interactive () {
git rebase--helper --make-script ${keep_empty:+--keep-empty} \
${rebase_merges:+--rebase-merges} \
+ ${rebase_cousins:+--rebase-cousins} \
$revisions ${restrict_revision+^$restrict_revision} >"$todo" ||
die "$(gettext "Could not generate todo list")"
diff --git a/git-rebase.sh b/git-rebase.sh
index a553f969d11..40be59ecc47 100755
--- a/git-rebase.sh
+++ b/git-rebase.sh
@@ -17,7 +17,7 @@ q,quiet! be quiet. implies --no-stat
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 @@ state_dir=
# One of {'', continue, skip, abort}, as parsed from command line
action=
rebase_merges=
+rebase_cousins=
preserve_merges=
autosquash=
keep_empty=
@@ -286,6 +287,15 @@ do
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 "$interactive_rebase" && interactive_rebase=implied
diff --git a/sequencer.c b/sequencer.c
index afa155c2829..e2f83942843 100644
--- a/sequencer.c
+++ b/sequencer.c
@@ -3578,6 +3578,7 @@ static int make_script_with_merges(struct pretty_print_context *pp,
unsigned flags)
{
int keep_empty = flags & TODO_LIST_KEEP_EMPTY;
+ int rebase_cousins = flags & TODO_LIST_REBASE_COUSINS;
struct strbuf buf = STRBUF_INIT, oneline = STRBUF_INIT;
struct strbuf label = STRBUF_INIT;
struct commit_list *commits = NULL, **tail = &commits, *iter;
@@ -3755,6 +3756,9 @@ static int make_script_with_merges(struct pretty_print_context *pp,
&commit->object.oid);
if (entry)
to = entry->string;
+ else if (!rebase_cousins)
+ to = label_oid(&commit->object.oid, NULL,
+ &state);
if (!to || !strcmp(to, "onto"))
fprintf(out, "%s onto\n", cmd_reset);
diff --git a/sequencer.h b/sequencer.h
index 6bc4da17243..d9570d92b11 100644
--- a/sequencer.h
+++ b/sequencer.h
@@ -60,6 +60,12 @@ int sequencer_remove_state(struct replay_opts *opts);
#define TODO_LIST_SHORTEN_IDS (1U << 1)
#define TODO_LIST_ABBREVIATE_CMDS (1U << 2)
#define TODO_LIST_REBASE_MERGES (1U << 3)
+/*
+ * When rebasing merges, commits that do have the base commit as ancestor
+ * ("cousins") are *not* rebased onto the new base by default. If those
+ * commits should be rebased onto the new base, this flag needs to be passed.
+ */
+#define TODO_LIST_REBASE_COUSINS (1U << 4)
int sequencer_make_script(FILE *out, int argc, const char **argv,
unsigned flags);
diff --git a/t/t3430-rebase-merges.sh b/t/t3430-rebase-merges.sh
index 1628c8dcc20..3d4dfdf7bec 100755
--- a/t/t3430-rebase-merges.sh
+++ b/t/t3430-rebase-merges.sh
@@ -176,6 +176,24 @@ test_expect_success 'with a branch tip that was cherry-picked already' '
EOF
'
+test_expect_success 'do not rebase cousins unless asked for' '
+ git checkout -b cousins master &&
+ before="$(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 &&
--
2.17.0.windows.1.33.gfcbb1fa0445
