nixpkgs/pkgs/development/tools/rufo/gemset.nix

{
  rufo = {
    groups = ["default"];
    platforms = [];
    source = {
      remotes = ["https://rubygems.org"];
      sha256 = "0nwasskcm0nrf7f52019x4fvxa5zckj4fcvf4cdl0qflrcwb1l9f";
      type = "gem";
    };
    version = "0.12.0";
  };
}