lint: update signed-off-by check

The current signed-off-by check doesn't really work well as a lint
stable test being run by the pre-commit git hook.  This test looks
at the PREVIOUS commit instead of the staged commit, which works well
on the server. In looking for a way to check the staged commit message,
I found the commit-msg hook, which is the correct way to check the
staged message.

- Update the commit message check from a lint-stable test to a
lint-extended test.
- Add the check for signed-off-by to the commit-msg hook

Change-Id: I8be8aef25730d988c7cf1586ae66ecb839d5f756
Signed-off-by: Martin Roth <martinroth@google.com>
Reviewed-on: https://review.coreboot.org/20920
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Chris Ching <chingcodes@chromium.org>

util/lint/lint-extended-020-signed-off-by

@@ -0,0 +1,23 @@
+#!/bin/sh
+# This file is part of the coreboot project.
+#
+# Copyright 2016 Google Inc.
+#
+# 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, or (at your option)
+# any later version.
+#
+# 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 a signed-off-by line on the latest git commit
+
+# This test is mainly for the jenkins server
+if [ -n "$(command -v git)" ] && [ -d .git ]; then
+	if [ -z "$(git log -n 1 | grep '[[:space:]]\+Signed-off-by: ')" ]; then
+		echo "No Signed-off-by line in commit message"
+	fi
+fi