pack-bitmap: fix leak of haves/wants object lists

When we do a bitmap-aware revision traversal, we create an object_list
for each of the "haves" and "wants" tips. After creating the result
bitmaps these are no longer needed or used, but we never free the list
memory.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

object.c

@@ -307,6 +307,15 @@ int object_list_contains(struct object_list *list, struct object *obj)
 	return 0;
 }
 
+void object_list_free(struct object_list **list)
+{
+	while (*list) {
+		struct object_list *p = *list;
+		*list = p->next;
+		free(p);
+	}
+}
+
 /*
  * A zero-length string to which object_array_entry::name can be
  * initialized without requiring a malloc/free.