prepare-commit-msg

#!/usr/bin/python3
#

import os
import subprocess
import sys

cherry_pick_file = ".git/CHERRY_PICK_HEAD"
if os.path.exists(cherry_pick_file):
  commit_msg_file = sys.argv[1]

  commit_msg = list(open(commit_msg_file, 'rt').readlines())
  cherry_pick = list(map(lambda l: l.strip(), open(cherry_pick_file, 'rt').readlines()))

  user = subprocess.run(["git", "config", "user.name"],
                        capture_output=True, check=True).stdout.strip().decode('utf8')
  first_comment=0
  for line in commit_msg:
    if line.startswith('#'):
      break
    else:
      first_comment += 1
  os.rename(commit_msg_file, commit_msg_file + ".bak")
  out = open(commit_msg_file, 'wt')
  for line in commit_msg[:first_comment]:
    out.write(line)
  out.write("\n")
  out.write(f"Cherry-picked from {cherry_pick[0][:8]} by {user}\n")
  for line in commit_msg[first_comment:]:
    out.write(line)