Just like with regular `pick` commands, if we are trying to recreate a
merge commit, we now test whether the parents of said commit match HEAD
and the commits to be merged, and fast-forward if possible.
This is not only faster, but also avoids unnecessary proliferation of
new objects.
Signed-off-by: Johannes Schindelin <johannes.schindelin@xxxxxx>
---
sequencer.c | 21 ++++++++++++++++++++-
1 file changed, 20 insertions(+), 1 deletion(-)
diff --git a/sequencer.c b/sequencer.c
index 567cfcbbe8b..a96255426e7 100644
--- a/sequencer.c
+++ b/sequencer.c
@@ -2085,7 +2085,7 @@ static int do_merge(struct commit *commit, const char *arg, int arg_len,
struct commit *head_commit, *merge_commit, *i;
struct commit_list *common, *j, *reversed = NULL;
struct merge_options o;
- int ret;
+ int can_fast_forward, ret;
static struct lock_file lock;
for (merge_arg_len = 0; merge_arg_len < arg_len; merge_arg_len++)
@@ -2151,6 +2151,14 @@ static int do_merge(struct commit *commit, const char *arg, int arg_len,
return error(_("Cannot merge without a current revision"));
}
+ /*
+ * If HEAD is not identical to the parent of the original merge commit,
+ * we cannot fast-forward.
+ */
+ can_fast_forward = commit && commit->parents &&
+ !oidcmp(&commit->parents->item->object.oid,
+ &head_commit->object.oid);
+
strbuf_addf(&ref_name, "refs/rewritten/%.*s", merge_arg_len, arg);
merge_commit = lookup_commit_reference_by_name(ref_name.buf);
if (!merge_commit) {
@@ -2164,6 +2172,17 @@ static int do_merge(struct commit *commit, const char *arg, int arg_len,
rollback_lock_file(&lock);
return -1;
}
+
+ if (can_fast_forward && commit->parents->next &&
+ !commit->parents->next->next &&
+ !oidcmp(&commit->parents->next->item->object.oid,
+ &merge_commit->object.oid)) {
+ strbuf_release(&ref_name);
+ rollback_lock_file(&lock);
+ return fast_forward_to(&commit->object.oid,
+ &head_commit->object.oid, 0, opts);
+ }
+
write_message(oid_to_hex(&merge_commit->object.oid), GIT_SHA1_HEXSZ,
git_path_merge_head(), 0);
write_message("no-ff", 5, git_path_merge_mode(), 0);
--
2.15.1.windows.2.1430.ga56c4f9e2a9
