github-arc.py

#!/usr/bin/python

import os
from collections import named_tuple
import re
import mailbox
import time
from subprocess import check_call, check_output
import tempfile

maildir_path = '.'
mbox = mailbox.Maildir(maildir_path)
handled = set()

user = 'haskell'
repo = 'ghc'

pull_re = re.compile(r'git pull (https:\/\/github.com/[\w\d-]+/[\w\d-]+) ([\w\d-]+)')

PullRequest = named_tuple('PullRequest', 'pull_repo pull_branch')

def parse_message(msg):
    to = msg.get('To')
    if to is None:
        raise RuntimeError('No To header, ignoring')

    m = re.find('%s/%s' % (user, repo), to)
    if m is None:
        raise RuntimeError('To header %s malformed, ignoring' % to)

    reply_to = msg.get('Reply-To')
    if reply_to is None:
        raise RuntimeError('No Reply-To header, ignoring')

    m = pull_re.find(msg.as_string())
    if m is None:
        raise RuntimeError("Couldn't find git pull command, ignoring")

    pull_repo = m.group(1)
    pull_branch = m.group(2)
    return PullRequest(pull_repo, pull_branch)
    
def handle_message(msg):
    pr = parse_message(msg)

    # TODO: Look up using git pull request API
    target_branch = ''

    tmp = tempfile.mkdtemp()
    repo_path = os.path.join(tmp, 'repo')
    check_call(['git', 'clone', repo_url, 'repo'], cwd=tmp)
    check_call(['git', 'remote', 'add', 'pr', pull_repo], cwd=repo_path)
    check_call(['git', 'remote', 'update', 'pr'], cwd=repo_path)
    merge_base = check_output(['git', 'merge-base',
                               'origin/%s' % target_branch,
                               'pr/%s' % pull_branch], cwd=repo_path)
    if merge_base == '':
        return

    os.rmdir(tmp)

    check_call(['git', 'checkout', 'pr/%s' % pull_branch], cwd=repo_path)
    arc_output = check_output(['arc', 'diff', '--never-amend', '--verbatim', merge_base])
    diff_id = 'D42' # TODO: parse arc output

    send_notification(diff_id)
    msg.set_flags('SR')

def send_notification(diff_id):
    diff_url = 'http://phabricator.haskell.org/differential/%s' %  diff_id
    msg = """
Hi ghc-newbie,

We've received your pull request on GitHub. Thanks! It's great that
you've contributed.

GHC, for a variety of well-considered reasons [1], uses a tool called
Phabricator [2] -- not GitHub -- to process contributions. We have
taken the liberty of posting your pull request to Phab for further
review. You can see it here: %s

If you have modifications to make, please use our Phab workflow,
documented in full here [3] and in brief here [4].

Thanks again, and we look forward to reviewing and hopefully merging
your patch!

 - The GHC team


[1]: <find appropriate destination>
[2]: http://phabricator.org/
[3]: https://ghc.haskell.org/trac/ghc/wiki/Phabricator
[4]: <find appropriate destination>
    """ % (diff_url)

    sendmail(reply_to, msg)

while True:
    for key,msg in mbox.items():
        if key in handled:
            continue

        try:
            handle_message(msg)
        except Exception as e:
            print "Encountered exception while handling message %s: %s" % (key,e)
        finally:
            handled.add(key)