generator(data, done) {
    const {last} = data;
    const binary = path.resolve(getDirname(import.meta.url), '../cli.js');

    execFile('node', [binary, last, '--help'], (error, out) => {
      if (error) {
        done(error);
        return;
      }

      const results = this.parseHelp(last, out);
      done(null, results);
    });
  }
Generator completion event done

@param {String}   data   Environment object as parsed by tabtab
@param {Function} done   Callback to invoke with completion results