Write git hash revision on file with grunt

gistfile1.txt

grunt.registerTask('tag-revision', 'Tag the current build revision', function () {
  grunt.task.requires('git-describe');

  grunt.file.write('public/version.json', JSON.stringify({
    version: grunt.config('pkg.version'),
    revision: grunt.config('meta.revision'),
    date: grunt.template.today()
  }));
});