A hook for git that inserts at the beginning of the commit message name of the current branch, if the message is empty (contains empty or comment lines).

prepare-commit-msg

#!/usr/bin/env python3
import sys
import subprocess
 
 
with open(sys.argv[1], 'r+') as commit_message_file:
    commit_message = list(commit_message_file)
 
    for line in commit_message:
        line = line.strip()
        if line and not line.startswith('#'):  # comment line
            break  # a non-empty line
    else:  # empty message
        try:
            branch_name = subprocess.check_output('git symbolic-ref --short HEAD', shell=True).strip().decode('utf-8')
        except subprocess.CalledProcessError:
            pass
        else:
            commit_message.insert(0, branch_name + ' ')
 
    commit_message_file.seek(0)
    for line in commit_message:
        commit_message_file.write(line)