Prefill the commit message by the branch name

prepare-commit-msg

#!/usr/bin/env python3

# Prefill the commit message + create changelog file by the branch name
# eg.:
# branch-name = PRO-<num ticket>-<type ticket>-<main subject>-<message>
# Type ticket: can be bugfix, tech, enhancement, other

# Eg.: PRO-1234-tech-document-split-size 
# --> commit message: Refs #PRO-1234 - document: split size
# --> create file: PRO-1234-tech-document-split-size.tech
#     Document: split size (#PRO-1234)

# Global Setup
# - create a `~/.git/hooks` folder
# - create the `prepare-commit-msg` hook file in this folder and paste this
#   script
# - chmod +x ~/.git/hooks/prepare-commit-msg
# - make git use this folder `git config --global core.hooksPath ~/.git/hooks`
# - allow for emtpy commit message: git commit --allow-empty-message (you can
#   create an alias)

import re
import sys
import subprocess

if __name__ == '__main__':
    
    try:
        branch_name = subprocess.check_output(
            ["git", "symbolic-ref", "--short", "HEAD"]).decode()
    except subprocess.CalledProcessError:
        branch_name = None
    
    if not branch_name:
        sys.exit()
    
    branch_name = branch_name.replace('\n', ' ')
    
    list_type = ["bugfix", "tech", "enhancement", "other"]
    
    result = re.match(
        "(?P<pro>PRO)-(?P<num>\d*)-(?P<type>({}))-(?P<app>\w*)-(?P<message>.*)".format("|".join(list_type)),
        branch_name)

    if result:
        num_commit = result.group("num")
        app = result.group("app")
        message = result.group("message").replace('-', ' ')
        type = result.group("type")
        
        # Set changelog message
        changelog_message = "{}: {} (#PRO-{})".format(
            app.title(), message, num_commit)
        
        # Create changelog file
        try:
            subprocess.Popen(
                ["bin/changelog", "add", type, changelog_message])
        except subprocess.CalledProcessError:
            print("Error create changelog")
            sys.exit()

        # Create commit message
        commit_messsage = "Refs #PRO-{} - {}: {}".format(
            num_commit, app, message)

        # Open, check and writte commit message
        commit_filepath = sys.argv[1]
        with open(commit_filepath, 'r+') as cf:
            # If first line has no message: exit program (avoid `git commit
            # --amend)
            if not cf.readline().strip():
                cfr = cf.read()
                cf.seek(0)
                cf.write('{}\n\n'.format(commit_messsage) + cfr)

Error message when rebase, we check HEAD and we are in detached HEAD... remove the message if possible

fatal: ref HEAD is not a symbolic ref