Merge branch 'os/commit-submodule-ignore' into maint

"git status" honored the ignore=dirty settings in .gitmodules but
"git commit" didn't.

* os/commit-submodule-ignore:
  commit: pay attention to submodule.$name.ignore in .gitmodules

Author: gitster

builtin/commit.c

@@ -1452,6 +1452,7 @@ int cmd_commit(int argc, const char **argv, const char *prefix)
 		usage_with_options(builtin_commit_usage, builtin_commit_options);
 
 	wt_status_prepare(&s);
+	gitmodules_config();
 	git_config(git_commit_config, &s);
 	determine_whence(&s);
 	s.colopts = 0;