code: function loadFiles(pattern, rootDir) {    
      // assert `pattern` is a valid glob (non-empty string) or array of globs
      var isString = typeof pattern === 'string';
      var isArray = Array.isArray(pattern);
      if ((!isString && !isArray) || (pattern.length === 0)) {
          throw new TypeError('A glob pattern or an array of glob patterns is required.');
      }
  
      // find all the gulpfiles - needs to happen synchronously so we create the tasks before gulp runs
      var filelist = resolveGlob(pattern, rootDir)
          .map(function(filename) {
              return path.relative(process.cwd(), path.join(rootDir, filename));
          });
  
      var subfiles = getSubfiles(filelist);
  
      // load all the gulpfiles
      subfiles.forEach(function (subfile) {
          util.log( 'Loading', util.colors.yellow(subfile.relativePath));
          loadSubfile(subfile, tasks);
      });
  }
docs: Load tasks from gulpfiles specified by the file `pattern`.
  @param {string|array} pattern - A gulp-style file pattern to glob gulpfiles