replace: plug a memory leak

Recent update to for_each_replace_name() to make it use a strbuf in
place of a fixed buffer forgot to release the memory held by the
strbuf before leaving the function.

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

builtin/replace.c

@@ -120,6 +120,7 @@ static int for_each_replace_name(const char **argv, each_replace_name_fn fn)
 		if (fn(full_hex, ref.buf, &oid))
 			had_error = 1;
 	}
+	strbuf_release(&ref);
 	return had_error;
 }