shallow clone: unparse and reparse an unshallowed commit

Otherwise we would not read the real parents from the commit
object.

upload-pack.c

@@ -582,6 +582,7 @@ static void receive_needs(void)
 				object->flags &= ~CLIENT_SHALLOW;
 				/* make sure the real parents are parsed */
 				unregister_shallow(object->sha1);
+				object->parsed = 0;
 				parse_commit((struct commit *)object);
 				parents = ((struct commit *)object)->parents;
 				while (parents) {