fmt-patch: Support --attach

This patch touches a couple of files, because it adds options to print a
custom text just after the subject of a commit, and just after the
diffstat.

[jc: made "many dashes" used as the boundary leader into a single
 variable, to reduce the possibility of later tweaks to miscount the
 number of dashes to break it.]

Signed-off-by: Johannes Schindelin <Johannes.Schindelin@gmx.de>
Signed-off-by: Junio C Hamano <junkio@cox.net>
diff --git a/show-branch.c b/show-branch.c
index bbe26c2..684ffd1 100644
--- a/show-branch.c
+++ b/show-branch.c
@@ -259,7 +259,7 @@
 	struct commit_name *name = commit->object.util;
 	if (commit->object.parsed)
 		pretty_print_commit(CMIT_FMT_ONELINE, commit, ~0,
-				    pretty, sizeof(pretty), 0, NULL);
+				    pretty, sizeof(pretty), 0, NULL, NULL);
 	else
 		strcpy(pretty, "(unavailable)");
 	if (!strncmp(pretty, "[PATCH] ", 8))