ui-patch: match git-format-patch(1) output

Using (DIFF_FORMAT_DIFFSTAT | DIFF_FORMAT_PATCH) causes Git to emit a
"---" line between the commit message and the body of the patch, which
fixes a regression introduced in commit 455b598 (ui-patch.c: Use
log_tree_commit() to generate diffs, 2013-08-20), prior to which we
inserted the "---" line ourselves.

DIFF_FORMAT_SUMMARY is added so that we match the output of
git-format-patch(1) without the "-p" option.

Signed-off-by: John Keeping <john@keeping.me.uk>

ui-patch.c

@@ -73,7 +73,8 @@ void cgit_print_patch(const char *new_rev, const char *old_rev,
 	rev.diff = 1;
 	rev.show_root_diff = 1;
 	rev.max_parents = 1;
-	rev.diffopt.output_format |= DIFF_FORMAT_PATCH;
+	rev.diffopt.output_format |= DIFF_FORMAT_DIFFSTAT |
+			DIFF_FORMAT_PATCH | DIFF_FORMAT_SUMMARY;
 	setup_revisions(ARRAY_SIZE(rev_argv), (const char **)rev_argv, &rev,
 			NULL);
 	prepare_revision_walk(&rev);