#!/bin/sh -euC
#
# Reject commit messages that do not conform to Conventional Commits.
#
# Enforces Conventional Commits v1.0.0 at the syntactic level.
#
# Upstream:	gitea.bp99.eu/bp99/git-hooks

subject="$(sed -n 1p "$1")"
second="$(sed -n 2p "$1")"

fail() {
	>&2 cat <<EOF
commit-msg: $1

  subject: $subject
  format: <type>[(<scope>)][!]: <description>

Bypass with: git commit --no-verify
EOF
	exit 1
}

# type, optional (scope), optional !, terminal ': ', non-emtpy desc
printf '%s' "$subject" | grep -Eq '^[[:alpha:]]+(\([^()]+\))?!?: .+' \
|| fail 'subject does not conform to Conventional Commits'

# Body must begin one blank line after description
[ -z "$second" ] || fail 'Line 2 must be blank'