text: var gulp = require('gulp');
  var concat = require('gulp-concat');
  var replace = require('gulp-replace');
  var insert = require('gulp-insert');
  
  module.exports.bundle = function(buildConfig, moduleName, outputFile, outputConfig,
      sfx) {
    var sfx = sfx || false;
    // loading it earlier interfers with custom traceur.
    var Builder = require('systemjs-builder');
    var builder = new Builder();
    builder.config(buildConfig);
    if (sfx) {
      return builder.buildSFX(moduleName, outputFile, outputConfig);
    } else {
      return builder.build(moduleName, outputFile, outputConfig);
    }
  };
  
  
  module.exports.modify = function(srcs, concatName) {
    return gulp.src(srcs)
      .pipe(concat(concatName))
      .pipe(replace('sourceMappingURL', 'sourceMappingURLDisabled'));  // TODO: add concat for sourceMaps
  };
  