format-patch: append --signature after notes

When appending a new signature with "format-patch --signature", if
the "--notes" option is also in effect, the location of the new
signature (and if the signature should be added in the first place)
should be decided using the contents of the original commit log
message, before the message from the notes is added.

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

log-tree.c

diff --git a/log-tree.c b/log-tree.c
index e7e08f4..4390b11 100644
--- a/log-tree.c
+++ b/log-tree.c
@@ -672,12 +672,14 @@
 	ctx.reflog_info = opt->reflog_info;
 	ctx.fmt = opt->commit_format;
 	pretty_print_commit(&ctx, commit, &msgbuf);
+
+	if (opt->add_signoff)
+		append_signoff(&msgbuf, opt->add_signoff);
+
 	if ((ctx.fmt != CMIT_FMT_USERFORMAT) &&
 	    ctx.notes_message && *ctx.notes_message)
 		strbuf_addstr(&msgbuf, ctx.notes_message);
 
-	if (opt->add_signoff)
-		append_signoff(&msgbuf, opt->add_signoff);
 	if (opt->show_log_size) {
 		printf("log size %i\n", (int)msgbuf.len);
 		graph_show_oneline(opt->graph);