Simple Flake

flake.nix

{
  inputs = {
    nixpkgs = {
      url = "github:nixos/nixpkgs/nixos-unstable";
    };
    flake-utils = {
      url = "github:numtide/flake-utils";
    };
  };
  outputs = { nixpkgs, flake-utils, ... }: flake-utils.lib.eachDefaultSystem (system:
    let
      pkgs = import nixpkgs {
        inherit system;
      };
      mg = (with pkgs; stdenv.mkDerivation {
          pname = "mg";
          version = "20220212";
          src = fetchFromGitHub {
            owner = "hboetes";
            repo = "mg";
            rev = "20220212";
            sha256 = "sha256-JeFNB+HdoQdIy5yz3jhta9VPdTdSIzXKkT7YQIrKWmA=";
          };
          makeFlags = [ "PKG_CONFIG=${buildPackages.pkg-config}/bin/${buildPackages.pkg-config.targetPrefix}pkg-config" ];
          nativeBuildInputs = [ pkgs.pkg-config ];
          buildInputs = [ pkgs.ncurses6 ];
          buildPhase = "make -j $NIX_BUILD_CORES";
          installPhase = ''
            mkdir -p $out/bin
            mv $TMP/mg/mg $out/bin
          '';
        }
      );
    in rec {
      defaultApp = flake-utils.lib.mkApp {
        drv = defaultPackage;
      };
      defaultPackage = mg;
      devShell = pkgs.mkShell {
        buildInputs = [
          mg
        ];
      };
    }
  );
}