title: Gulp sourcemap with less/concat/autoprefixer/minifycss?
body: <p>Is it possible to generate a sourcemap with all these transformations?</p>
  
  <pre><code>gulp.task('styles', function() {
      return gulp.src(source.styles)
          .pipe(plumber())
          .pipe(gulpif(/\.less$/, plumber().pipe(less({
              strictMath: true,
              strictUnits: true,
          }))))
          .pipe(concat('bundle.css'))
          .pipe(prefixer(['last 2 versions', '&gt; 1%', 'ie 9'], {cascade: false}))
          .pipe(minifyCss())
          .pipe(gulp.dest('public/css'));
  });
  </code></pre>
  
  <p>Libraries used:</p>
  
  <ul>
  <li><a href="https://github.com/plus3network/gulp-less">gulp-less</a></li>
  <li><a href="https://github.com/robrich/gulp-if">gulp-if</a></li>
  <li><a href="https://github.com/wearefractal/gulp-concat">gulp-concat</a></li>
  <li><a href="https://github.com/Metrime/gulp-autoprefixer">gulp-autoprefixer</a></li>
  <li><a href="https://github.com/jonathanepollack/gulp-minify-css">gulp-minify-css</a></li>
  </ul>
  
  <p>I know <a href="http://lesscss.org/usage/#command-line-usage-source-map-output-filename">less</a> can generate sourcemaps, gulp-concat I don't think supports them, <a href="https://github.com/ai/autoprefixer">autoprefixer</a> is supposed to preserve them, and minify-css/<a href="https://github.com/GoalSmashers/clean-css">clean-css</a> don't seem to make any mention of source maps. Am I out of luck?</p>