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merge: use repo_in_merge_bases for octopus up-to-date check 

The octopus merge path checks whether each remote head is already
an ancestor of HEAD by computing all merge-bases via
repo_get_merge_bases() and comparing the first result's OID to
the remote head.  This is more expensive than necessary:
repo_get_merge_bases() calls paint_down_to_common() with
min_generation=0, performs the full STALE drain, and may run
remove_redundant(), when all we need is a yes/no reachability
answer.

Replace this with repo_in_merge_bases(), which answers the
is-ancestor question directly.  When generation numbers are
available, repo_in_merge_bases() uses can_all_from_reach() -- a
DFS bounded by generation number that stops as soon as the target
is found or ruled out, without entering paint_down_to_common() at
all.  Without generation numbers, it still benefits from a tighter
min_generation floor.

Signed-off-by: Kristofer Karlsson <krka@spotify.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
main
Kristofer Karlsson 2026-05-12 06:11:26 +00:00 committed by Junio C Hamano
parent 29bd7ed512
commit 0acbaf9000
2 changed files with 14 additions and 14 deletions
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18
builtin/merge.c
View File

@ -1735,21 +1735,11 @@ int cmd_merge(int argc,
struct commit_list *j;

for (j = remoteheads; j; j = j->next) {
struct commit_list *common_one = NULL;
struct commit *common_item;

/*
* Here we *have* to calculate the individual
* merge_bases again, otherwise "git merge HEAD^
* HEAD^^" would be missed.
*/
if (repo_get_merge_bases(the_repository, head_commit,
j->item, &common_one) < 0)
int ret = repo_in_merge_bases(the_repository,
j->item, head_commit);
if (ret < 0)
exit(128);

common_item = common_one->item;
commit_list_free(common_one);
if (!oideq(&common_item->object.oid, &j->item->object.oid)) {
if (!ret) {
up_to_date = 0;
break;
}

10
t/t6408-merge-up-to-date.sh
View File

@ -89,4 +89,14 @@ test_expect_success 'merge fast-forward octopus' '
test "$expect" = "$current"
'

test_expect_success 'merge octopus already up to date' '

git reset --hard c2 &&
test_tick &&
git merge c0 c1 &&
expect=$(git rev-parse c2) &&
current=$(git rev-parse HEAD) &&
test "$expect" = "$current"
'

test_done