nix-book/source/shell-recipes/0250-shell-with-flake-rev.nix

with (import <nixpkgs> {});
let
   hello = (builtins.getFlake git+https://codeberg.org/mhwombat/hello-flake?ref=main&rev=3aa43dbe7be878dde7b2bdcbe992fe1705da3150).packages.${builtins.currentSystem}.default;
in
mkShell {
  buildInputs = [
    hello
  ];
}