git-fetch-pr.py

#!/usr/bin/env python3
import sys
import re
import argparse
import subprocess
import requests


def get_remote_owner_repo(remote):
    "Returns the github owner and repo of the remote"
    cmd = ['git', 'config', 'remote.{}.url'.format(remote)]
    url = subprocess.check_output(cmd, universal_newlines=True)
    url = url.strip()
    match = re.match(r'^[email protected]:([^/]+)/(.+)$', url)
    if not match:
        raise ValueError('invalid remote url {}'.format(url))
    owner, repo = match.groups()
    if repo.endswith('.git'):
        repo = repo[:-len('.git')]
    return owner, repo


def fetch_pr(remote, pr):
    "Fetches the PR into FETCH_HEAD"
    cmd = ['git', 'fetch', '-q', remote, 'pull/{0}/head'.format(pr)]
    subprocess.check_call(cmd)


def get_latest_pr_tag(pr):
    "Returns the latest PR tag, if any. Otherwise, None"
    cmd = ['git', 'tag', '-l', 'pr/{}-*'.format(pr)]
    out = subprocess.check_output(cmd, universal_newlines=True)
    out = out.strip()
    if not out:
        return None, None
    out = out.split('\n')
    out.sort()
    match = re.match(r'(.+)-v(\d+)$', out[-1])
    base, version = match.groups()
    return base, int(version)


def get_pr_info(owner, repo, pr):
    url = 'https://api.github.com/repos/{}/{}/pulls/{}'.format(owner, repo, pr)
    r = requests.get(url)
    if r.status_code == 404:
        raise ValueError('No such PR {}/{}/{}'.format(owner, repo, pr))
    r.raise_for_status()
    return r.json()


def make_tag(name, head):
    cmd = ['git', 'tag', name, head]
    subprocess.check_call(cmd)


def main(args, prog=None):
    p = argparse.ArgumentParser(prog=prog)
    p.add_argument('remote')
    p.add_argument('pr', type=int)
    args = p.parse_args(args)
    owner, repo = get_remote_owner_repo(args.remote)
    pr_info = get_pr_info(owner, repo, args.pr)
    tag_base, tag_version = get_latest_pr_tag(args.pr)
    if not tag_base:
        default_tag_base = pr_info['head']['ref']
        tag_base = input('Branch name [{}]: '.format(default_tag_base))
        if not tag_base:
            tag_base = default_tag_base
        tag_base = 'pr/{}-{}'.format(args.pr, tag_base)
        tag_version = 0
    tag_version += 1
    fetch_pr(args.remote, args.pr)
    tag_name = '{}-v{}'.format(tag_base, tag_version)
    make_tag(tag_name, 'FETCH_HEAD')
    print('Created tag', tag_name)


if __name__ == '__main__':
    sys.exit(main(sys.argv[1:], sys.argv[0]))