run git command with nodejs

gitexec.js

const {exec} = require('child_process');

function git(args) {
  return new Promise(res => {
    exec('git ' + args, (err, stdout, stderr) => {
      if (err) {
        throw err;
      } else {
        res(stdout.trim());
      }
    });
  });
}

await git('fetch upstream');