{ pkgs ? import <nixpkgs> {} }:
pkgs.mkShell {
  nativeBuildInputs = with pkgs; [
    nixFlakes
  ];

  NIX_CONF_DIR = let
    current = pkgs.lib.optionalString (builtins.pathExists /etc/nix/nix.conf)
      (builtins.readFile /etc/nix/nix.conf);

    nixConf = pkgs.writeTextDir "opt/nix.conf" ''
      ${current}
      experimental-features = nix-command flakes ca-references
    '';
  in
    "${nixConf}/opt";
}