pack-objects: fix early eviction for max depth delta objects

The 'depth' variable doesn't reflect the actual maximum depth used
when other objects already depend on the current one.

Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin-pack-objects.c

@@ -1486,7 +1486,7 @@ static void find_deltas(struct object_entry **list, unsigned *list_size,
 		 * depth, leaving it in the window is pointless.  we
 		 * should evict it first.
 		 */
-		if (entry->delta && depth <= n->depth)
+		if (entry->delta && max_depth <= n->depth)
 			continue;
 
 		/*