commit-msg

#!/usr/bin/env python3
# Commit message hook for Git repos.
# Andrew Benson (28-July-2021) — ported to Python

import re
import sys

GREEN = '\033[1;32m'
RED   = '\033[1;31m'
RESET = '\033[0m'


def ok(msg):
    print(f"{GREEN}\u2714 {RESET}{msg}")


def fail(msg):
    print(f"{RED}\u2715 {RESET}{msg}")
    sys.exit(1)


def main():
    message_file = sys.argv[1]

    with open(message_file, encoding='utf-8') as fh:
        lines = fh.readlines()

    first_line = lines[0] if lines else ''

    # Enforce conventional commits (https://www.conventionalcommits.org)
    ## Header line format
    header_re = re.compile(r'^([a-zA-Z0-9]+)(\([a-zA-Z0-9]+\))?(!?):\s\S')
    m = header_re.match(first_line)
    if m:
        ok('Commit message does follow Conventional Commits format'
           ' (https://www.conventionalcommits.org)')
    else:
        fail('Commit message does not follow Conventional Commits format'
             ' (https://www.conventionalcommits.org)')

    type_    = m.group(1)
    breaking = m.group(3)

    ## Type is valid
    valid_types = {'fix', 'feat', 'build', 'docs', 'style',
                   'test', 'refactor', 'perf', 'clean'}
    if type_ in valid_types:
        ok('Type is valid (https://www.conventionalcommits.org)')
    else:
        fail('Type is invalid (https://www.conventionalcommits.org)')

    ## BREAKING CHANGE consistency
    breaking_found = any(re.match(r'^BREAKING\sCHANGE:\s', line) for line in lines)

    if breaking == '!' and not breaking_found:
        fail("'BREAKING CHANGE' footer missing"
             ' (https://www.conventionalcommits.org)')
    elif breaking_found and breaking != '!':
        fail("'BREAKING CHANGE' footer present but '!' missing from header"
             ' (https://www.conventionalcommits.org)')
    else:
        ok('Consistent breaking change status'
           ' (https://www.conventionalcommits.org)')


if __name__ == '__main__':
    main()