update-index: fix cache entry leak in add_one_file()

When we fail to add the cache entry to the index, we end up
just leaking the struct. We should follow the pattern of the
early-return above and free it.

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

builtin/update-index.c

@@ -287,8 +287,10 @@ static int add_one_path(const struct cache_entry *old, const char *path, int len
 	}
 	option = allow_add ? ADD_CACHE_OK_TO_ADD : 0;
 	option |= allow_replace ? ADD_CACHE_OK_TO_REPLACE : 0;
-	if (add_cache_entry(ce, option))
+	if (add_cache_entry(ce, option)) {
+		free(ce);
 		return error("%s: cannot add to the index - missing --add option?", path);
+	}
 	return 0;
 }