am: fix commit buffer leak in get_commit_info()

Calling logmsg_reencode() may allocate a buffer for the
commit message (because we need to load it from disk, or
because it needs re-encoded). We must "unuse" it afterwards
to free it.

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

builtin/am.c

@@ -1417,6 +1417,7 @@ static void get_commit_info(struct am_state *state, struct commit *commit)
 		die(_("unable to parse commit %s"), oid_to_hex(&commit->object.oid));
 	state->msg = xstrdup(msg + 2);
 	state->msg_len = strlen(state->msg);
+	unuse_commit_buffer(commit, buffer);
 }
 
 /**