let nixpkgs-pin = builtins.fromJSON (builtins.readFile ./nixpkgs.json); nixpkgs-src = builtins.fetchTarball nixpkgs-pin; nixpkgs = import nixpkgs-src { }; in { pkgs ? nixpkgs }: pkgs.mkShell { NIX_PATH = "nixpkgs=${nixpkgs.path}"; buildInputs = [ pkgs.morph ]; }