code: function copyBase(src, dest, options, callback) {
    if (typeof options !== 'object') {
      callback = options;
      options = {};
    }
  
    if (arguments.length < 3) {
      return invalid.apply(null, arguments);
    }
  
    var fs = utils.fs; // graceful-fs (lazyily required)
    var opts = utils.extend({overwrite: true}, options);
    var cb = once(callback);
    var listener = once(ws);
    src = path.resolve(src);
  
    var rs = fs.createReadStream(src)
      .on('error', handleError('read', src, opts, cb))
      .once('readable', listener)
      .on('end', listener);
  
    function ws() {
      mkdir(dest, function(err) {
        if (err) return cb(err);
        rs.pipe(fs.createWriteStream(dest, writeOpts(opts))
          .on('error', handleError('write', dest, opts, cb))
          .on('close', handleClose(src, dest, cb)));
      });
    }
  }
docs: Copy a file from `src` to `dest`
  
  @param {String} `src` Source filepath
  @param {String} `dest` Destination filepath
  @param {Object} `options`
  @param {Function} `cb` Callback function
  @api public