Make 'git fsck' complain about non-commit branches

Since having non-commits in branches is a no-no, and just means you cannot
commit on them, let's make fsck tell you when a branch is bad.
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

builtin-fsck.c

@@ -555,20 +555,23 @@ static int fsck_handle_reflog(const char *logname, const unsigned char *sha1, in
 	return 0;
 }
 
+static int is_branch(const char *refname)
+{
+	return !strcmp(refname, "HEAD") || !prefixcmp(refname, "refs/heads/");
+}
+
 static int fsck_handle_ref(const char *refname, const unsigned char *sha1, int flag, void *cb_data)
 {
 	struct object *obj;
 
-	obj = lookup_object(sha1);
+	obj = parse_object(sha1);
 	if (!obj) {
-		if (has_sha1_file(sha1)) {
-			default_refs++;
-			return 0; /* it is in a pack */
-		}
 		error("%s: invalid sha1 pointer %s", refname, sha1_to_hex(sha1));
 		/* We'll continue with the rest despite the error.. */
 		return 0;
 	}
+	if (obj->type != OBJ_COMMIT && is_branch(refname))
+		error("%s: not a commit", refname);
 	default_refs++;
 	obj->used = 1;
 	mark_reachable(obj, REACHABLE);