Submodules: Use "ignore" settings from .gitmodules too for diff and status

The .gitmodules file is parsed for "submodule.<name>.ignore" entries
before looking for them in .git/config. Thus settings found in .git/config
will override those from .gitmodules, thereby allowing the local developer
to ignore settings given by the remote side while also letting upstream
set defaults for those users who don't have special needs.

Signed-off-by: Jens Lehmann <Jens.Lehmann@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/diff-index.c

@@ -3,6 +3,7 @@
 #include "commit.h"
 #include "revision.h"
 #include "builtin.h"
+#include "submodule.h"
 
 static const char diff_cache_usage[] =
 "git diff-index [-m] [--cached] "
@@ -17,6 +18,7 @@ int cmd_diff_index(int argc, const char **argv, const char *prefix)
 	int result;
 
 	init_revisions(&rev, prefix);
+	gitmodules_config();
 	git_config(git_diff_basic_config, NULL); /* no "diff" UI options */
 	rev.abbrev = 0;