{pkgs, ...}: {
  system.activationScripts.nixClosureDiff = {
    supportsDryActivation = true;
    text = ''
      # show which packages changed versions or are new/removed in this upgrade
      # source: <https://github.com/luishfonseca/dotfiles/blob/32c10e775d9ec7cc55e44592a060c1c9aadf113e/modules/upgrade-diff.nix>
      ${pkgs.nvd}/bin/nvd --nix-bin-dir=${pkgs.nix}/bin diff /run/current-system "$systemConfig"
    '';
  };
}