tag referring to a commit but not directly?

[Junio C Hamano <junkio@cox.net>]

I was playing with a tag that refers to another tag which refers
to a commit, and found out that some things did not work as I
expected.

Is it a PEBCAK on my part to expect tag-to-tag-to-commit to
behave the same way as a bare commit (or a tag to commit), or is
this just a bug?  I think the following two would fix what I
found, but I am not sure if I am using the "struct object" and
friends the way they are expected to be used.  I am uncertain
about what the expected behaviour should be either for that
matter; I admit that tags are new to me.

---

*** To find whom to ask about the thing I am butchering, I
*** used the following pickaxe:

git-rev-list linus |
git-diff-tree --stdin -v -s \
-S'	if (obj->type == tag_type)
		obj = ((struct tag *)obj)->tagged;'

git-rev-list linus |
git-diff-tree --stdin -v -s \
-S'	/*
	 * Tag object? Look what it points to..
	 */
	if (object->type == tag_type) {'

------------
cd /opt/packrat/playpen/public/in-place/git/git.junio/
jit-diff 0:5
# - master: format-patch: fix skipping of blank-lines (take 2)
# + 5: tag deref until we get non tag
diff --git a/commit.c b/commit.c
--- a/commit.c
+++ b/commit.c
@@ -52,8 +52,9 @@ struct commit *lookup_commit_reference(c
 
 	if (!obj)
 		return NULL;
-	if (obj->type == tag_type)
-		obj = ((struct tag *)obj)->tagged;
+	while (obj->type == tag_type)
+		obj = parse_object(((struct tag *)obj)->tagged->sha1);
+
 	return check_commit(obj, sha1);
 }
 
diff --git a/rev-list.c b/rev-list.c
--- a/rev-list.c
+++ b/rev-list.c
@@ -354,12 +354,12 @@ static struct commit *get_commit_referen
 	/*
 	 * Tag object? Look what it points to..
 	 */
-	if (object->type == tag_type) {
+	while (object->type == tag_type) {
 		struct tag *tag = (struct tag *) object;
 		object->flags |= flags;
 		if (tag_objects && !(object->flags & UNINTERESTING))
 			add_pending_object(object, tag->tag);
-		object = tag->tagged;
+		object = parse_object(tag->tagged->sha1);
 	}
 
 	/*

Compilation finished at Sat Jul  9 02:37:16