gulpfile.babel.js

gulp.task('exec', async () => {
  const exec = {
    exec(command, options) {
      return new Promise((resolve, reject) => {
        cp.spawn(command, options, {stdio: 'inherit'}).on('error', reject).on('exit', resolve);
      });
    },

    async local(commands) {
      await this.exec(process.env.SHELL, ['-c', commands.join('&&')]);
    },

    async remote(commands) {
      await this.exec('ssh', [process.env.REMOTE_HOST, commands.join('&&')]);
    },
  };

  await exec.local([
    'pwd',
    'ls',
  ]);

  await exec.remote([
    'pwd',
    'ls',
  ]);
});

old.gulpfile.babel.js

gulp.task('exec', () => {
  const exec = {
    exec(command, options) {
      return new Promise((resolve, reject) => {
        cp.spawn(command, options, {stdio: 'inherit'}).on('error', reject).on('exit', resolve);
      });
    },

    local(commands) {
      return this.exec(process.env.SHELL, ['-c', commands.join('&&')]);
    },

    remote(commands) {
      return this.exec('ssh', [process.env.REMOTE_HOST, commands.join('&&')]);
    },
  };

  exec.local([
    'pwd',
    'ls',
  ]).then(() => {
    return exec.remote([
      'pwd',
      'ls',
    ]);
  }).catch(err => {
    console.error(err.stack);
  });
});