nix-helpers: 473a71e91f4928ed95e43f42728a2d8cead6af05

     1: { }:
     2: with builtins;
     3: with {
     4:   nixpkgs = with tryEval <nixpkgs>;
     5:     if success then value else abort "Don't have <nixpkgs>?!";
     6: };
     7: 
     8: new: env:
     9: env // {
    10:   NIX_PATH = "nixpkgs=${toString new}:real=${toString nixpkgs}";
    11: }