old_contents: /* jshint node:true */
  
  'use strict';
  
  var CssComb       = require('csscomb'),
      csscomb       = new CssComb(),
      gutil         = require('gulp-util'),
      transform     = require('stream').Transform,
      bufferstreams = require('bufferstreams'),
  
      PLAGIN_NAME   = 'gulp-csscomb';
  
  module.exports = function () {
  
      var stream = new transform({ objectMode: true });
  
      stream._transform = function(file, unused, done) {
          // Pass through if null
          if (file.isNull()) {
              stream.push(file);
              done();
              return;
          }
  
          if (file.isStream()) {
              file.contents = file.contents.pipe(new bufferstreams(function (err, buffer, cb) {
                  if (err) {
                      cb(gutil.PluginError(PLAGIN_NAME, err));
                  }
                  var output = csscomb.processString(String(buffer));
                  cb(null, new Buffer(output));
              }));
              stream.push(file);
              done();
          } else {
              var css = String(file.contents);
              gutil.log(css);
              var output = csscomb.processString(css);
              file.contents = new Buffer(output);
              stream.push(file);
              done();
          }
      };
  
      return stream;
  };
new_contents: /* jshint node:true */
  
  'use strict';
  
  var CssComb       = require('csscomb'),
      csscomb       = new CssComb(),
      gutil         = require('gulp-util'),
      transform     = require('stream').Transform,
      bufferstreams = require('bufferstreams'),
  
      PLAGIN_NAME   = 'gulp-csscomb';
  
  module.exports = function () {
  
      var stream = new transform({ objectMode: true });
  
      stream._transform = function(file, unused, done) {
          // Pass through if null
          if (file.isNull()) {
              stream.push(file);
              done();
              return;
          }
  
          if (file.isStream()) {
              file.contents = file.contents.pipe(new bufferstreams(function (err, buffer, cb) {
                  if (err) {
                      cb(gutil.PluginError(PLAGIN_NAME, err));
                  }
                  var syntax = file.path.split('.').pop();
                  var output = csscomb.processString(String(buffer), syntax);
                  cb(null, new Buffer(output));
              }));
              stream.push(file);
              done();
          } else {
              var syntax = file.path.split('.').pop();
              var output = csscomb.processString(String(file.contents), syntax);
              file.contents = new Buffer(output);
              stream.push(file);
              done();
          }
      };
  
      return stream;
  };
subject: Add file extension check