git-rewrite-author

#!/usr/bin/env python

"""Rewrite author/committer history of a git repository

Have you ever accidentally committed to a git repository with a broken
user config?  No?  But your co-workers have?

So, you're stuck with commits like this::

    Author: root <root@localhost>

        Hotfix on the production server.  This was urgent!

Nasty.  Or::

    Author: John Doe <john@localhost>

        Fixed bug #1.  Committed on my laptop.

Would it be nice to rewrite history?  And take care of committers, as
well as of authors?  Without all the hassle?  Now, you can!

Usage::

    $ git-rewrite-author -w "John Doe <john@localhost>" "John Doe <dearjohn@example.com>"

You're not sure which authors/committers are hidden in your repository?
What about::

    $ git-rewrite-author -l

Tags are rewritten automagically, too!

Enjoy!

"""
import argparse
import re
import subprocess
import textwrap


description = "Rewrite author/committer in git history"
epilog = """
Example:

$ git-rewrite-author -w "Name <me@localhost>" "Full Name <me@example.com>"
"""

git_rewrite_command = """git filter-branch --env-filter 'if [ "$GIT_AUTHOR_NAME" = "%s" -a "$GIT_AUTHOR_EMAIL" = "%s" ]; then GIT_AUTHOR_NAME="%s"; GIT_AUTHOR_EMAIL="%s"; fi; export GIT_AUTHOR_NAME; export GIT_AUTHOR_EMAIL' --tag-name-filter cat -f -- --all"""
git_log_command = "git log --pretty=full"


def parse_args():
    """Parse command-line arguments"""

    parser = argparse.ArgumentParser(description=description,
                         epilog=epilog,
                         formatter_class=argparse.RawDescriptionHelpFormatter)
    parser.add_argument('-l', '--list', action='store_true',
                        help="List all authors and committers")
    parser.add_argument('-w', '--rewrite', nargs=2,
                        metavar=('old', 'new'), type=str,
                        help="Rewrite authors and committers")
    return parser.parse_args()


def main(args):
    """Rewrite history using args"""

    if args.list:
        list_git_authors()
    elif args.rewrite:
        old_name, old_email = parse_author_arg(args.rewrite[0])
        new_name, new_email = parse_author_arg(args.rewrite[1])

        rewrite_git_author(old_name, old_email, new_name, new_email)
        rewrite_git_committer(old_name, old_email, new_name, new_email)
    else:
        print "Doing nothing.  Invoke with -h for help."


def parse_author_arg(arg):
    """Parse name/email argument"""

    name, email = re.match("([A-Za-z0-9\(\)\.\- ]+) <(.*)>", arg).groups()
    return name, email


def rewrite_git_author(old_name, old_email, new_name, new_email):
    """Rewrite author history in git"""

    command = git_rewrite_command % (old_name, old_email, new_name,
                                     new_email)
    subprocess.call(command, shell=True)


def rewrite_git_committer(old_name, old_email, new_name, new_email):
    """Rewrite committer history in git"""

    command = git_rewrite_command.replace('AUTHOR', 'COMMITTER') % \
                (old_name, old_email, new_name, new_email)
    subprocess.call(command, shell=True)


def list_git_authors():
    """List authors and committers"""

    output = subprocess.check_output(git_log_command.split(' '))
    matches = re.findall('(Author|Commit): (.*)\n', output)
    names = [u[1] for u in matches]
    unique_names = sorted(set(names))

    print "The following authors and committers have contributed:"
    print
    for name in unique_names:
        print name


if __name__ == '__main__':
    args = parse_args()
    main(args)