with import "${builtins.getEnv "_NIX_TEST_BUILD_DIR"}/config.nix";

mkDerivation {
  name = "filter";
  builder = builtins.toFile "builder" "ln -s $input $out";
  input =
    builtins.path {
      path = ((builtins.getEnv "TEST_ROOT") + "/filterin");
      filter = path: type:
           type != "symlink"
        && baseNameOf path != "foo"
        && !((import ./lang/lib.nix).hasSuffix ".bak" (baseNameOf path));
    };
}