git status: ignoring untracked files must apply to submodules too

Since 1.7.0 submodules are considered dirty when they contain untracked
files. But when git status is called with the "-uno" option, the user
asked to ignore untracked files, so they must be ignored in submodules
too. To achieve this, the new flag DIFF_OPT_IGNORE_UNTRACKED_IN_SUBMODULES
is introduced.

Signed-off-by: Jens Lehmann <Jens.Lehmann@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/wt-status.c b/wt-status.c
index e0e915e..5848f1c 100644
--- a/wt-status.c
+++ b/wt-status.c
@@ -304,6 +304,8 @@
 	setup_revisions(0, NULL, &rev, NULL);
 	rev.diffopt.output_format |= DIFF_FORMAT_CALLBACK;
 	DIFF_OPT_SET(&rev.diffopt, DIRTY_SUBMODULES);
+	if (!s->show_untracked_files)
+		DIFF_OPT_SET(&rev.diffopt, IGNORE_UNTRACKED_IN_SUBMODULES);
 	rev.diffopt.format_callback = wt_status_collect_changed_cb;
 	rev.diffopt.format_callback_data = s;
 	rev.prune_data = s->pathspec;