GeezerVison

def get_branch_name():
    return subprocess.check_output(
        [
            'git',
            'rev-parse',
            '--abbrev-ref',
            'HEAD',
        ],
    ).decode('UTF-8')


def get_ticket_id_from_branch_name(branch_name):
    return re.findall('^[A-Z]{1,10}-[0-9]{1,5}', branch_name)[0]


def main():
    if os.environ.get('GIT_EDITOR') == ':':
        # According to git docs, the editor will not show, e.g. because
        # of a `git commit -m "..."` supplied message. Therefore don't touch
        # the commit message as there is no opportunity for the user to edit it
        return

    jira = JIRA(server=JIRA_SERVER)

    branch_name = get_branch_name()
    ticket_id = get_ticket_id_from_branch_name(branch_name)

    issue = jira.issue(ticket_id)
    summary = issue.fields.summary

    with io.open(sys.argv[1], 'r+') as f:
        contents = f.readlines()
        contents.insert(0, u'{} - {}\n'.format(ticket_id, summary))
        f.seek(0, 0)
        f.writelines(contents)

ABC-123 - Replace Foo with Bar

# Please enter the commit message for your changes. Lines starting
# with '#' will be ignored, and an empty message aborts the commit.