Forbid to push remote branches specified with an environment variable "GIT_PROTECTED_BRANCHES".

pre-push.py

#!/usr/bin/env python3
# coding: utf-8

def main():
    import sys

    local_ref, local_sha1, remote_ref, remote_sha1 = sys.stdin.readline().split()
    remote_branch = extract_branch(remote_ref)

    if remote_branch in list_protected_branches():
        message = 'Cannot push to protected branch.'
        print(message, end = '\n\n', file = sys.stderr)
        sys.exit(1)


def extract_branch(remote_ref):
    return remote_ref.split('refs/heads/', 1).pop()


def list_protected_branches():
    import os
    return os.environ.get('GIT_PROTECTED_BRANCHES', '').split()


if __name__ == '__main__':
    main()