docs: function firstCommit(dir, cb) {
    if (typeof dir === 'function') {
      return firstCommit(process.cwd(), dir);
    }
    if (typeof cb !== 'function') {
      throw new TypeError('expected callback to be a function');
    }
  
    lazy.git(dir).log(function(err, history) {
      if (err) return cb(err);
  
      history.sort(function(a, b) {
        return b.date.localeCompare(a.date);
      });
  
      cb(null, history[history.length - 1]);
    });
  }