index.js
function (options) {

        var me = this;
        var filter = options && options.filter;

        return me.custom(function (file, callback) {

            if (!filter || !filter(file)) {

                var filePath = file.path;
                var hash = me.hashMap[ filePath ];

                hash = md5(file.contents);
                me.hashMap[ filePath ] = hash;

            }

            callback();

        });

    }
function (options) {

        var me = this;
        var filter = options && options.filter;

        return me.custom(function (file, callback) {

            if (!filter || !filter(file)) {

                var filePath = file.path;
                var hash = me.hashMap[ filePath ];

                hash = md5(file.contents);
                me.hashMap[ filePath ] = hash;

            }

            callback();

        });

    }
分析文件的 hash

@param {Object} options
@property {Function=} options.filter 文件过滤