old_contents: /* eslint: no-console 0 */
  
  import gulp from 'gulp';
  import useref from 'gulp-useref';
  import gulpif from 'gulp-if';
  import uglify from 'gulp-uglify';
  import autoprefixer from 'gulp-autoprefixer';
  import cssnano from 'gulp-cssnano';
  import htmlmin from 'gulp-htmlmin';
  import runSequence from 'run-sequence';
  import Builder from 'systemjs-builder';
  
  gulp.task('bundle', (done) => {
    let builder = new Builder('app/public');
    builder.bundle('scripts/main.js', 'app/dist/application.min.js', {
      minify: true,
      config: {
        defaultJSExtensions: 'js'
      }
    }).then(() => done()).catch(done);
  });
  
  // build for production: concatenate, minify
  gulp.task('build', (done) => {
    runSequence('clean', 'compile', 'bundle', () => {
      gulp.src(['app/public/*[!lib]*/*.html', 'app/public/*.html'])
        .pipe(useref())
        .pipe(gulpif(['*.js', '!vendor/*.js'], uglify()))
        .pipe(gulpif(['*.css', '!vendor/*.css'], autoprefixer()))
        .pipe(gulpif(['*.css', '!vendor/*.css'], cssnano()))
        .pipe(gulpif('*.html', htmlmin({ collapseWhitespace: true })))
        .pipe(gulp.dest('app/dist'))
        .on('end', done);
    });
  });
  
new_contents: /* eslint: no-console 0 */
  
  import gulp from 'gulp';
  import useref from 'gulp-useref';
  import gulpif from 'gulp-if';
  import uglify from 'gulp-uglify';
  import autoprefixer from 'gulp-autoprefixer';
  import cssnano from 'gulp-cssnano';
  import htmlmin from 'gulp-htmlmin';
  import runSequence from 'run-sequence';
  import Builder from 'systemjs-builder';
  
  gulp.task('bundle', (done) => {
    let builder = new Builder('app/src');
    builder.bundle('scripts/main.js', 'app/dist/application.min.js', {
      minify: true,
      config: {
        defaultJSExtensions: 'js'
      }
    }).then(() => done()).catch(done);
  });
  
  // build for production: concatenate, minify
  gulp.task('build', (done) => {
    runSequence('clean', 'compile', 'bundle', () => {
      gulp.src(['app/public/*[!lib]*/*.html', 'app/public/*.html'])
        .pipe(useref())
        .pipe(gulpif(['*.js', '!vendor/*.js'], uglify()))
        .pipe(gulpif(['*.css', '!vendor/*.css'], autoprefixer()))
        .pipe(gulpif(['*.css', '!vendor/*.css'], cssnano()))
        .pipe(gulpif('*.html', htmlmin({ collapseWhitespace: true })))
        .pipe(gulp.dest('app/dist'))
        .on('end', done);
    });
  });
  
subject: Update bundle task