code: function readMainFiles(path, files) {
  		fs.readdirSync(path).forEach(function (filename) {
  			var file = path+'/'+filename,
  				file_ext = filename.slice(filename.lastIndexOf('.') + 1);
  			if (file_ext==='css' || file_ext==='scss') {
  				files.push(file.slice(path_main_len)); //把“main/”也去掉
  			} else if (filename[0]!=='.' && fs.statSync(file).isDirectory()) {
  				//排除.svn，.github之类的文件夹
  				readMainFiles(file, files);
  				//在构建目录的main和min里创建对应的目录
  				file = file.slice(path_main_len)+'/';
  				util.mkdir(path_main, file);
  				util.mkdir(path_min, file);
  				version_file || util.mkdir(path_tag, file);
  			}
  		});
  	}
docs: 读取main下的所有入口文件名，遇到子目录则在构建目录里创建相应的子目录