[Bioc-devel] How can I maintain a stable list of source urls

Hi
I am working to make bioconductor packages available through the nix
package manager (https://nixos.org/). Currently nixpkgs points to a source
url on one of the bioconductor mirrors. nixpkgs tracks the url and a sha256
hash of the unpacked source link. Unfortunately the links themselves often
disappear as the packages get updated either due to a version number change
or changes inside the repo that affect the hash output. This breaks
corresponding nix package. This happens even for stable bioconductor
versions like 3.10. nixpkgs aims for reproducible builds, which means when
things change, the url should reflect the change too and the contents
behich old urls should be preserved long enough to manage the  change. Do
you have any suggestions short of rebuilding a bioconductor mirror with
immutable urls?

Thanks,
TIm