Git commit message hook that checks for issue number within your commit message if you're on a bug branch. To enable: add this file into your repo's `.git/hooks` directory and make it executable (`chmod +x commit-msg`)

commit-msg

#!/usr/bin/env python

import sys, os, re
from subprocess import check_output

# Collect the parameters
commit_msg_filepath = sys.argv[1]

# Figure out which branch we're on
branch = check_output(['git', 'symbolic-ref', '--short', 'HEAD']).strip()

# Check the commit message if we're on an issue branch
if branch.startswith('bug/i'):
    print "commit-msg: Bug branch detected (%s)." % branch
    result = re.match('bug/i(.*)', branch)
    issue_number = result.group(1)
    required_message = "#%s" % issue_number

    with open(commit_msg_filepath, 'r') as f:
        content = f.read()
        if required_message not in content:
            print "commit-msg: WARNING: Commit message omits issue number (%s)" % required_message
            sys.exit(1)