util/lint: Add filename checker

Check that filenames have only alphanumeric characters plus underscore,
dash, and period.

Change-Id: I7bf0be15d588aa1a5ece628b56e871662d6af44b
Signed-off-by: Martin Roth <gaumless@gmail.com>
Reviewed-on: https://review.coreboot.org/26938
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Werner Zeh <werner.zeh@siemens.com>
Reviewed-by: Patrick Georgi <pgeorgi@google.com>

util/lint/lint-stable-023-filenames

@@ -0,0 +1,24 @@
+#!/bin/sh
+# This file is part of the coreboot project.
+#
+# Copyright (C) 2018 Google LLC
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; version 2 of the License.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# DESCR: Check for illegal characters in filename
+
+LC_ALL=C export LC_ALL
+
+# Skip check if git isn't available
+if [ -n "$(command -v git)" ] && \
+	[ "$(git rev-parse --is-inside-work-tree 2>/dev/null)" = "true" ]
+then
+	git ls-files | grep "[^A-Za-z0-9/_\.-]"
+fi