Git hook to auto prefix commit message with story/feature ID/name.

prepare-commit-msg

#!/usr/bin/env python

"""
Copy-paste this to `.git/hooks/prepare-commit-msg` and make the file executable.
Then just write your commit message as `git commit -m "message"`.
"""

from subprocess import check_output
import sys


# Set your feature branch prefix here.
FEATURE_BRANCH_PREFIX = 'feature/'


def get_branch_name():
    # Credits: https://stackoverflow.com/a/11868440/4183498.
    return check_output('git symbolic-ref --short HEAD'.split()).strip()


def get_commit_prefix():
    branch_name = get_branch_name()

    if FEATURE_BRANCH_PREFIX not in branch_name:
        return ''

    # Assuming feature branch name format `<prefix>myfeature-123-description`.
    branch_name_parts = branch_name.split(FEATURE_BRANCH_PREFIX)
    # Will extract `myfeature-123`.
    feature_id = '-'.join(branch_name_parts[-1].split('-', 2)[:2])

    return feature_id + ': '


def prefix_commit_message(commit_message_file):
    commit_prefix = get_commit_prefix()
    if not commit_prefix:
        return

    with open(commit_message_file, 'r') as commit_message:
        lines = commit_message.readlines()

    lines[0] = commit_prefix + lines[0]

    with open(commit_message_file, 'w') as commit_message:
        commit_message.write(''.join(lines))


if __name__ == '__main__':
    prefix_commit_message(sys.argv[1])