prepare-commit-msg

#!/usr/bin/env python3
import sys
import subprocess

import hooks_cfg as cfg

pcm_cfg = cfg.checks_cfg['prepare-commit-message']


def get_branchname():
    """Get current branch name."""
    # print('before')
    try:
        branchname = subprocess.check_output(
            # -q suppress error message for non-symbolic (detached) ref.
            ['/usr/bin/git', 'symbolic-ref', '-q', '--short', 'HEAD'])
    except subprocess.CalledProcessError as e:
        # When `fatal: ref HEAD is not a symbolic ref`. It would return
        # code 128 indicating this, but because we are using `-q`
        # it does return generic error code 1.
        if e.returncode == 1:
            return False
        else:
            raise
    # Convert to string.
    branchname = branchname.decode('utf-8')
    return branchname.strip()


def prepend_commit_msg(text, prefix='', suffix=''):
    """Prepend commit message with text."""
    with open(sys.argv[1], 'r+') as f:
        msg = f.read()
        # Prepend only if message is empty or message does not contain
        # same text already and start of message is either new line or
        # comment.
        if not msg or (text not in msg and msg[0] in ('\n', '#')):
            # Point to start of file.
            f.seek(0)
            f.write(prefix+text+suffix+msg)
            # Truncate to overwrite file.
            f.truncate()


# We prefix with two empty lines to have commit message look like this
# (when initially message is empty):

#
#
# [BRANCH] BRANCH_NAME

# Check if branch should be excluded to not update its commit message.
branchname = get_branchname()
if branchname and branchname not in pcm_cfg['exclude_branches']:
    prepend_commit_msg('[BRANCH] %s' % branchname, prefix='\n\n')