yarn 2 bootstrap downloader, when you don't want to commit yarn's binary to git

bootstrap.cjs

const target = './releases/yarn-berry.cjs';
// Change URL to refer to specific commit if you want version to be locked
const url = 'https://github.com/yarnpkg/berry/raw/master/packages/berry-cli/bin/berry.js';

const Path = require('path')
const fs = require('fs')
const targetPath = Path.join(__dirname, target)
if(fs.existsSync(targetPath)) {
  require(targetPath)
} else {
  const https = require('https')
  const util = require('util')

  https.get(url).on('response', r => {
    https.get(r.headers.location).on('response', r => {
      const buffers = []
      r.on('data', d => {
        buffers.push(d)
      }).on('end', () => {
        fs.writeFileSync(targetPath, Buffer.concat(buffers));
        require(target)
      })
    })
  })
}