[PATCH v2 2/2] revision: Implement `git log --merge` also for rebase/cherry_pick/revert

[Michael Lohmann <mi.al.lohmann@gmail.com>]

Co-authored-by: Johannes Sixt <j6t@kdbg.org>
Signed-off-by: Michael Lohmann <mi.al.lohmann@gmail.com>
---

> I won't comment on the coding style violations in the patch below in
> this message.

I hope this one is better. The other one was just a proof of the general
concept and meant as a starting point for a discussion if this is wanted
at all. But I should still have taken more care.

On 12. Jan 2024, at 08:35, Johannes Sixt <j6t@kdbg.org> wrote:
> Ha! Very nice patch. For comparison, have a look at my patch to achieve
> the same that I never submitted (in particular, the author date):
> https://github.com/j6t/git/commit/2327526213bc2fc3c109c1d8b4b0d95032346ff0
> 
> This implementation is more complete than mine. I like it.

Ha! Nice one! I took a few of your changes as an inspiration and put you
as a co-author.

Cheers
Michael

Difference compared to v1: Basically complete rewrite using
"refs_resolve_ref_unsafe". Has to be applied after [PATCH v2 1/2] to
avoid conflict.

 revision.c | 27 ++++++++++++++++++++-------
 1 file changed, 20 insertions(+), 7 deletions(-)

diff --git a/revision.c b/revision.c
index 786e1a3e89..b0b47dd241 100644
--- a/revision.c
+++ b/revision.c
@@ -1961,6 +1961,25 @@ static void add_pending_commit_list(struct rev_info *revs,
 	}
 }
 
+static const char *lookup_other_head(struct object_id *oid)
+{
+	struct ref_store *refs = get_main_ref_store(the_repository);
+	const char *name;
+	int i;
+	static const char *const other_head[] = {
+		"MERGE_HEAD", "REBASE_HEAD", "CHERRY_PICK_HEAD", "REVERT_HEAD"
+	};
+
+	for (i = 0; i < ARRAY_SIZE(other_head); i++) {
+		name = refs_resolve_ref_unsafe(refs, other_head[i],
+					       RESOLVE_REF_READING, oid, NULL);
+		if (name)
+			return name;
+	}
+
+	die("--merge without MERGE_HEAD, REBASE_HEAD, CHERRY_PICK_HEAD or REVERT_HEAD?");
+}
+
 static void prepare_show_merge(struct rev_info *revs)
 {
 	struct commit_list *bases;
@@ -1974,13 +1993,7 @@ static void prepare_show_merge(struct rev_info *revs)
 	if (repo_get_oid(the_repository, "HEAD", &oid))
 		die("--merge without HEAD?");
 	head = lookup_commit_or_die(&oid, "HEAD");
-	other_head = refs_resolve_ref_unsafe(get_main_ref_store(the_repository),
-					     "MERGE_HEAD",
-					     RESOLVE_REF_READING,
-					     &oid,
-					     NULL);
-	if (!other_head)
-		die("--merge without MERGE_HEAD?");
+	other_head = lookup_other_head(&oid);
 	other = lookup_commit_or_die(&oid, other_head);
 	add_pending_object(revs, &head->object, "HEAD");
 	add_pending_object(revs, &other->object, other_head);
-- 
2.43.0.284.g6c31128a96