getSourceCode = (gitUrl, tag, outPath) => {
  fs.ensureDirSync(outPath);

  const args = [
    'clone',
    '--branch', tag,
    '--depth', '1',
    '--config', 'advice.detachedHead=false',
    gitUrl,
    outPath,
  ];
  return wfHelper.promisedExec(`git ${args.join(' ')}`);
}
Get the source code from a tag from a git repo.
@param {string} gitUrl URL to git repo.
@param {string} tag The tag to get.
@param {string} outPath Path to write the source code to