title: Gulp 4 multiple tasks on same source and in series
body: <p>I edit my gulpfile like below:</p>
  
  <pre><code>gulp.task('watch', function() {
      gulp.watch('**/*.html', gulp.series('htmlcomb'));
      gulp.watch('css/**/*.scss', gulp.series('csscomb'));
      gulp.watch('css/**/*.scss', gulp.series('cssmin'));        
      gulp.watch('js/**/*.js', gulp.series('jsmin'));
  });
  </code></pre>
  
  <p>But when I run gulp watch it stops after csscomb. When I edit a scss file. It only comb on it.</p>
  
  <p>I can run htmlcomb, jsmin and (cssbomb + cssmin) as async. But I need to run cssmin after csscomb.</p>