Prepend JIRA ticket name in commit message

prepare-commit-msg

#!/usr/bin/python
"""
This is a prepare-commit-msg hook for use with Jira

Copy this file to $GITREPOSITORY/.git/hooks/prepare-commit-msg

It will prepend PROJ-123 to your commit message, assuming your branch is
named proj-123.

"""
import re
import subprocess
import sys


def is_ticket(s):
    regex = r"[a-zA-Z]+-\d+"
    return re.match(regex, s)


def get_ticket():
    """Return the ticket id associated with the current feature branch"""
    branchname = subprocess.check_output(["git", "rev-parse",
                                          "--abbrev-ref", "HEAD"]).rstrip()
    if not is_ticket(branchname):
        raise ValueError("Branch name not in expected format")
    return branchname.upper()


def prepend_commit_msg(text):
    """Prepend the commit message with `text`"""
    msgfile = sys.argv[1]

    with open(msgfile) as f:
        contents = f.read()

    with open(msgfile, 'w') as f:
        # Don't append if it's already there
        if not contents.startswith(text):
            f.write(text)
        f.write(contents)


def main():
    # Fail silently
    try:
        ticket = get_ticket()
        header = "{} ".format(ticket)
        prepend_commit_msg(header)
    except:
        # Swallow exceptions to handle branches
        # that don't follow the convention
        pass

if __name__ == '__main__':
    main()