I’m looking to include unstable version of uv, which according to search.nixos.org is 0.4.30
But i can’t find it in Nix package versions. Edit: Reason is, it gets updated only every 5 weeks 
What is an other way to get the right url, ref, sha256 and so one for using it with fetchTarball or fetchGit?
Btw, i also tried a link to a tarball from to official release tags, which is valid working url (e.g. https://github.com/NixOS/nixpkgs/archive/refs/tags/25.05-pre.tar.gz) but nix says:
fatal: repository 'https://github.com/NixOS/nixpkgs/archive/refs/tags/25.05-pre.tar.gz/' not found