revision: propagate flag bits from tags to pointees

With the previous fix 895c5ba3 (revision: do not peel tags used in
range notation, 2013-09-19), handle_revision_arg() that processes
command line arguments for the "git log" family of commands no
longer directly places the object pointed by the tag in the pending
object array when it sees a tag object.  We used to place pointee
there after copying the flag bits like UNINTERESTING and
SYMMETRIC_LEFT.

This change meant that any flag that is relevant to later history
traversal must now be propagated to the pointed objects (most often
these are commits) while starting the traversal, which is partly
done by handle_commit() that is called from prepare_revision_walk().
We did propagate UNINTERESTING, but did not do so for others, most
notably SYMMETRIC_LEFT.  This caused "git log --left-right v1.0..."
(where "v1.0" is a tag) to start losing the "leftness" from the
commit the tag points at.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

revision.c

@@ -273,6 +273,7 @@ static struct commit *handle_commit(struct rev_info *revs, struct object *object
 				return NULL;
 			die("bad object %s", sha1_to_hex(tag->tagged->sha1));
 		}
+		object->flags |= flags;
 	}
 
 	/*
@@ -284,7 +285,6 @@ static struct commit *handle_commit(struct rev_info *revs, struct object *object
 		if (parse_commit(commit) < 0)
 			die("unable to parse commit %s", name);
 		if (flags & UNINTERESTING) {
-			commit->object.flags |= UNINTERESTING;
 			mark_parents_uninteresting(commit);
 			revs->limited = 1;
 		}
@@ -302,7 +302,6 @@ static struct commit *handle_commit(struct rev_info *revs, struct object *object
 		if (!revs->tree_objects)
 			return NULL;
 		if (flags & UNINTERESTING) {
-			tree->object.flags |= UNINTERESTING;
 			mark_tree_contents_uninteresting(tree);
 			return NULL;
 		}
@@ -314,13 +313,10 @@ static struct commit *handle_commit(struct rev_info *revs, struct object *object
 	 * Blob object? You know the drill by now..
 	 */
 	if (object->type == OBJ_BLOB) {
-		struct blob *blob = (struct blob *)object;
 		if (!revs->blob_objects)
 			return NULL;
-		if (flags & UNINTERESTING) {
-			blob->object.flags |= UNINTERESTING;
+		if (flags & UNINTERESTING)
 			return NULL;
-		}
 		add_pending_object(revs, object, "");
 		return NULL;
 	}

t/t6000-rev-list-misc.sh

@@ -62,4 +62,15 @@ test_expect_success 'propagate uninteresting flag down correctly' '
 	test_cmp expect actual
 '
 
+test_expect_success 'symleft flag bit is propagated down from tag' '
+	git log --format="%m %s" --left-right v1.0...master >actual &&
+	cat >expect <<-\EOF &&
+	> two
+	> one
+	< another
+	< that
+	EOF
+	test_cmp expect actual
+'
+
 test_done