Hexo 'Clean' Gulp Task

//cleans cache file (db.json) and generated files (public_dir)
gulp.task('site:clean', (cb) => {
    const command = 'clean';
    const args = {};

    return hexo.init().then(() => {
        return hexo.call(command, args);
    }).then(() => {
        return cb()
    }).catch((err) => {
        hexo.error(err);

        return cb(err);
    });
});