Move MD5sum to the end of the dcf

This is a workaround for bug in pak: r-universe-org/help#556

routes/cache.js

@@ -34,7 +34,7 @@ export default function(req, res, next){
     res.set('Cache-Control', `public, max-age=60, stale-while-revalidate=${cdn_cache}`);
 
     if(doc){
-      const revision = 3; // bump to invalidate all caches
+      const revision = 4; // bump to invalidate all caches
       const etag = `W/"${doc._id}${revision}"`;
       const date = new Date(doc._published.getTime() + revision * 1000).toUTCString();
       res.set('ETag', etag);

src/tools.js

@@ -148,10 +148,11 @@ function unpack_deps(x){
 
 export function doc_to_dcf(doc){
   //this clones 'doc' and then deletes some fields
-  const { _id, _fileid, _type, Distro, ...x } = unpack_deps(doc);
+  const { _id, _fileid, _type, Distro, MD5sum, ...x } = unpack_deps(doc);
   if(_type == 'linux'){
     x.Platform = 'x86_64-pc-linux-gnu' //pak likes this to identify binaries
   }
+  x.MD5sum = MD5sum; //workaround for https://github.com/r-lib/pak/issues/733
   let keys = Object.keys(x);
   return keys.map(function(key){
     let val = x[key];