git.py

import os
from os import path
import subprocess


def describe(directory=None):
    if directory:
        cwd = os.getcwd()
        os.chdir(directory)

    ret = subprocess.run(
        ['git', 'show', '--no-patch', '--date=short', '--format=%cd.%h'],
        stdin=subprocess.PIPE, stdout=subprocess.PIPE, universal_newlines=True)

    if directory:
        os.chdir(cwd)

    ret.check_returncode()
    return ret.stdout.strip().replace('-', '')


def clone(url, directory):
    return_code = subprocess.call(['git', 'clone', url, directory])
    if return_code != 0:
        raise Exception(f'Failed to clone {url}')


def sync(cache_dir, repo_url, message=None):
    cwd = os.getcwd()
    devnull = open(os.devnull, 'wb')

    # Ensure git-sync tool is available.
    git_sync_dir = path.join(cache_dir, 'git-sync')
    git_sync_exec = path.join(git_sync_dir, 'git-sync')
    if not path.exists(git_sync_dir):
        os.makedirs(git_sync_dir)
        clone('https://github.com/simonthum/git-sync.git', git_sync_dir)
    else:
        os.chdir(git_sync_dir)
        subprocess.call(['git', 'pull', 'origin', 'master'], stdout=devnull, stderr=devnull)

    repo_name = path.basename(path.normpath(repo_url))
    repo_dir = path.join(cache_dir, repo_name)
    if not path.exists(repo_dir):
        os.makedirs(repo_dir)
        clone(repo_url, repo_dir)

        os.chdir(repo_dir)
        subprocess.call(['git', 'config', '--bool', 'branch.master.sync', 'true'])
        subprocess.call(['git', 'config', '--bool', 'branch.master.syncNewFiles', 'true'])
        if message:
            subprocess.call(['git', 'config', 'branch.master.syncCommitMsg', message])

    os.chdir(repo_dir)
    return_code = subprocess.call([git_sync_exec])
    if return_code != 0:
        raise Exception(f'failed to sync {repo_name}')

    os.chdir(cwd)

    return repo_dir