I use plan.json to generate Flatpak manifests. Flatpak expects immutable sources fixed by hashes, e.g.:

{
  "url": "https://hackage.haskell.org/package/integer-logarithms-1.0.3/integer-logarithms.cabal",
  "type": "file",
  "sha256": "21cdc5661958a703303d2b430220908db8c2c42dbc58db0d7baac1d171f31768"
}

However, the Cabal file may change due to an update to the Cabal file. Thus I would actually need to specifiy the URL:
https://hackage.haskell.org/package/integer-logarithms-1.0.3/revision/1.cabal

But plan.json does not tell the revision where its pkg-cabal-sha256 refers to.
Please add the revision number to plan.json.
Or is there an easy way to retrieve this information from 01-index.tar and friends?