Godot v3.x-simula with flake.nix on other repo

flake.nix

{
  inputs = {
    nixpkgs.url = "github:nixos/nixpkgs/63dacb46bf939521bdc93981b4cbb7ecb58427a0";
    systems.url = "github:nix-systems/x86_64-linux";
    godot = {
      url   = "git+https://github.com/haruki7049/godot?rev=df193d656aad69c0efe33fa9278907c2341d7ce9&submodules=1";
      flake = true;
    };
    flake-parts = {
      url = "github:hercules-ci/flake-parts";
      inputs.nixpkgs-lib.follows = "nixpkgs";
    };
    treefmt-nix = {
      url = "github:numtide/treefmt-nix";
      inputs.nixpkgs.follows = "nixpkgs";
    };
  };

  outputs =
    inputs:
    inputs.flake-parts.lib.mkFlake { inherit inputs; } {
      systems = import inputs.systems;

      imports = [ inputs.treefmt-nix.flakeModule ];

      perSystem = { pkgs, system, ... }: {
        packages.default = inputs.godot.packages."${system}".godot;

        devShells.default = pkgs.mkShell {
          packages = [ pkgs.nil ];
        };
      };
    };
}