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/diff.h b/diff.h
index 95ed7f8..6a71013 100644
--- a/diff.h
+++ b/diff.h
@@ -70,6 +70,7 @@
 #define DIFF_OPT_DIFF_FROM_CONTENTS  (1 << 22)
 #define DIFF_OPT_SUBMODULE_LOG       (1 << 23)
 #define DIFF_OPT_DIRTY_SUBMODULES    (1 << 24)
+#define DIFF_OPT_IGNORE_UNTRACKED_IN_SUBMODULES (1 << 25)
 
 #define DIFF_OPT_TST(opts, flag)    ((opts)->flags & DIFF_OPT_##flag)
 #define DIFF_OPT_SET(opts, flag)    ((opts)->flags |= DIFF_OPT_##flag)