#!/bin/sh

# SPDX-License-Identifier: GPL-2.0-or-later

# A hook script to prevent pushing unsuitable commits to the master branch.
# Unsuitable commits are commits that contain a local changelog below a '---'
# line. The criteria may get extended later.
#
# Information about the commits which are being pushed is supplied as lines to
# the standard input in the form:
#
#   <local ref> <local sha1> <remote ref> <remote sha1>

z40=0000000000000000000000000000000000000000

while read -r local_ref local_sha remote_ref remote_sha
do
	if [ "$remote_ref" != refs/heads/master ]
	then
		continue
	fi

	# The remote master branch should never get deleted by this push, so we
	# can assume that local_sha is not 0's. We may however be creating the
	# remote branch, when pushing to a new empty repository for instance.
	if [ "$remote_sha" = $z40 ]
	then
		# New branch, examine all commits
		range="$local_sha"
	else
		# Update to existing branch, examine new commits
		range="$remote_sha..$local_sha"
	fi

	#
	# Find invalid commits.
	#
	errors=0
	for commit in $(git rev-list "$range")
	do
		msg=$(git cat-file commit "$commit")

		# 1. The commit message shall not contain a local changelog.
		if echo "$msg" | grep -q '^--- *$'
		then
			echo >&2 "Found local changelog in commit $commit"
			errors=$((errors+1))
		fi

		# 2. The commit message shall have a Signed-off-by line
		# corresponding the committer.
		committer=$(echo "$msg" | grep '^committer ' | head -1 | \
				cut -d ' ' -f 2- | rev | cut -d ' ' -f 3- | rev)
		if ! echo "$msg" | grep -F -q "Signed-off-by: ${committer}"
		then
			echo >&2 "Missing committer Signed-off-by in commit $commit"
			errors=$((errors+1))
		fi

		# 3. A Reviewed-by or Acked-by is required.
		if ! echo "$msg" | grep -q '^\(Reviewed\|Acked\)-by: '
		then
			echo >&2 "No Reviewed-by or Acked-by in commit $commit"
			errors=$((errors+1))
		fi
	done

	if [ $errors != 0 ]
	then
		echo >&2 "Found $errors errors in $local_ref, not pushing"
		exit 1
	fi
done

exit 0