Gulpfile.js CSS Hashing

gulpfile.js

var gulp = require('gulp');
var clean = require('gulp-clean');
var rev = require('gulp-rev');
var inject = require('gulp-inject');
var fs = require('fs');
var jsonCss;

gulp.task('default', ['delete']);

gulp.task('cssHash', function() {
  return gulp.src('./css/styles.css')
    .pipe(gulp.dest('./css/dist'))
    .pipe(rev())
    .pipe(gulp.dest('./css/dist'))
    .pipe(rev.manifest())
    .pipe(gulp.dest('./css/dist/'));
});

gulp.task('inject', ['cssHash'], function() {
  jsonCss = JSON.parse(fs.readFileSync('./css/dist/rev-manifest.json'));
  var target = gulp.src('./index.html');
  var source = gulp.src('./css/dist/' + jsonCss['styles.css'], {read: false});
  return target.pipe(inject(source, {relative: true}))
    .pipe(gulp.dest(''));
});

gulp.task('delete', ['inject'], function () {
  return gulp.src(['css/dist/*.css', '!css/dist/' + jsonCss['styles.css']])
    .pipe(clean());
});

gulp.task('watch', function() {
  gulp.watch('css/styles.css', ['delete']);
});