isomorphic git proxy on Cloudflare Workers

isomorphic-git-cors-proxy.js

addEventListener('fetch', e => e.respondWith(handle(e.request)))

const ok = (req,u)=>{
  const q=u.searchParams
  return req.method==='OPTIONS'||
    (req.method==='GET' && u.pathname.endsWith('/info/refs') &&
      ['git-upload-pack','git-receive-pack'].includes(q.get('service')))||
    (req.method==='POST'&&u.pathname.endsWith('git-upload-pack')  &&
      req.headers.get('content-type')==='application/x-git-upload-pack-request')||
    (req.method==='POST'&&u.pathname.endsWith('git-receive-pack') &&
      req.headers.get('content-type')==='application/x-git-receive-pack-request')
}

async function handle(req){
  const src=new URL(req.url)
  if(!ok(req,src)) return new Response('Forbidden',{status:403})

  const target='https://'+src.pathname.slice(1)+src.search   // drop leading “/”

  if(req.method==='OPTIONS')
    return new Response(null,{status:200,headers:cors(req)})

  const resp=await fetch(target,{
    method:req.method,
    headers:strip(req.headers),
    body:req.body,
    redirect:'follow'
  })
  return new Response(resp.body,{
    status:resp.status,
    headers:merge(resp.headers,cors(req))
  })
}

const cors=req=>{
  const hdr=req.headers
  return {
    'Access-Control-Allow-Origin': hdr.get('Origin')||'*',
    'Access-Control-Allow-Methods':'GET,POST,OPTIONS',
    'Access-Control-Allow-Headers': hdr.get('Access-Control-Request-Headers')||'*',
    'Vary':'Origin'
  }
}

const strip=h=>{
  const out=new Headers(h)
  ;['host','origin','referer','content-length'].forEach(k=>out.delete(k))
  return out
}
const merge=(h,x)=>{const o=new Headers(h);for(const[k,v]of Object.entries(x))o.set(k,v);return o}

proxy for isomorphic git which is MUCH FASTER than the default one, and using it avoid sending your git credentials to a third party. CloudFlare workers are scale to zere and globally distributed, making it a great choice for a low traffic but demanding workload.

Used for
https://observablehq.com/@tomlarkworthy/jumpgate

I just pasted the code in the Cloudflare Workers console, ultra quick and simple to setup.

short video walkthrough https://www.youtube.com/watch?v=Nrc4xHZx80E (1m20)