code: function addFiles(sources, dest, options) {
        var opt = _.extend({}, defaultOptions, options || {});
  
        if(_.isString(sources)) {
          sources = [sources];
        }
  
        if(!inCwd(dest) || _.any(sources, function(src) {
          return !inCwd(src);
        })) {
          grunt.verbose.writeln('Ignore %s to %s: not in CWD.');
          return;
        }
  
        return addToQueueCopy(sources, dest, opt);
      }
docs: Allow transform stream to add files during transformation
  process to the copy/concat queue
  Path in cwd is required for security reason
  
  @param {Array|String} sources
  @param {String}       dest