util/lint: Introduce linter for git sign-off-by line

For compliance and to check if the commit message matches the
development guidelines, add a linter checking for the sign-off-by line
in the commit message. Also, hook it up to the test_build.sh script
which is used for CI builds.

These scripts were copied from the coreboot repository and were adjusted
so that they work for flashrom.

Original-Signed-off-by: Felix Singer <felixsinger@posteo.net>
Original-Reviewed-on: https://review.coreboot.org/c/flashrom/+/70079
Original-Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Original-Reviewed-by: Edward O'Callaghan <quasisec@chromium.org>

Change-Id: I03f1827803f8492d60a0a44174d5822c2265bfcb
Signed-off-by: Felix Singer <felixsinger@posteo.net>
Reviewed-on: https://review.coreboot.org/c/flashrom/+/70243
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Edward O'Callaghan <quasisec@chromium.org>
---
M test_build.sh
A util/lint/helper_functions.sh
A util/lint/lint-extended-020-signed-off-by
3 files changed, 101 insertions(+), 0 deletions(-)

diff --git a/test_build.sh b/test_build.sh
index 69d3a34..813d0b9 100755
--- a/test_build.sh
+++ b/test_build.sh
@@ -26,6 +26,11 @@
 fi
 
 
+run_linter() {
+	./util/lint/lint-extended-020-signed-off-by
+}
+
+
 build_make () {
 	make clean
 	make -j $(nproc) CONFIG_EVERYTHING=yes
@@ -67,5 +72,7 @@
 }
 
 
+run_linter
+
 build_make
 build_meson
diff --git a/util/lint/helper_functions.sh b/util/lint/helper_functions.sh
new file mode 100644
index 0000000..7abdab8
--- /dev/null
+++ b/util/lint/helper_functions.sh
@@ -0,0 +1,45 @@
+#!/usr/bin/env sh
+#
+# SPDX-License-Identifier: GPL-2.0-only
+
+# This file is sourced by the linters so that each one doesn't have to
+# specify these routines individually
+
+LC_ALL=C export LC_ALL
+
+if [ -z "$GIT" ]; then
+	GIT="$(command -v git)"
+else
+	# If git is specified, Do a basic check that it runs and seems like
+	# it's actually git
+	if ! "${GIT}" --version | grep -q git; then
+		echo "Error: ${GIT} does not seem to be valid."
+		exit 1;
+	fi
+fi
+
+if [ "$(${GIT} rev-parse --is-inside-work-tree 2>/dev/null)" = "true" ]; then
+	IN_GIT_TREE=1
+else
+	IN_GIT_TREE=0
+fi
+
+if [ "${IN_GIT_TREE}" -eq 1 ] && [ -z "${GIT}" ]; then
+	echo "This test needs git to run.  Please install it, then run this test again."
+	exit 1
+fi
+
+# Use git ls-files if the code is in a git repo, otherwise use find.
+if [ "${IN_GIT_TREE}" -eq 1 ]; then
+	FIND_FILES="${GIT} ls-files"
+else
+	FIND_FILES="find "
+	FINDOPTS="-type f"
+fi
+
+# Use git grep if the code is in a git repo, otherwise use grep.
+if [ "${IN_GIT_TREE}" -eq 1 ]; then
+	GREP_FILES="${GIT} grep"
+else
+	GREP_FILES="grep -r"
+fi
diff --git a/util/lint/lint-extended-020-signed-off-by b/util/lint/lint-extended-020-signed-off-by
new file mode 100755
index 0000000..ef62a45
--- /dev/null
+++ b/util/lint/lint-extended-020-signed-off-by
@@ -0,0 +1,23 @@
+#!/usr/bin/env sh
+# SPDX-License-Identifier: GPL-2.0-or-later
+#
+# DESCR: Check for a signed-off-by line on the latest commit
+
+
+LINTDIR="$(
+  cd -- "$(dirname "$0")" > /dev/null 2>&1 || return
+  pwd -P
+)"
+
+# shellcheck source=helper_functions.sh
+. "${LINTDIR}/helper_functions.sh"
+
+if [ "${IN_GIT_TREE}" -eq 0 ]; then
+	exit 0
+fi
+
+# This test is mainly for the jenkins server
+if ! ${GIT} log -n 1 | grep -q '[[:space:]]\+Signed-off-by: '; then
+	echo "No Signed-off-by line in commit message"
+	exit 1
+fi

