anchor.diff:  rec {
   
     
  -  nixpkgsRel = "nixpkgs-0.12pre9486";
  +  nixpkgsRel = "nixpkgs-0.12pre10056";
   
   
     configuration = {
  
positive.code:     environment = {
        extraPackages = pkgs: [
          pkgs.vim
        ];
      };
     
  
negative.code:   # Get a recent copy of Nixpkgs.
    nixpkgsTarball = pkgs.fetchurl {
      url = configuration.installer.nixpkgsURL + "/" + nixpkgsRel + ".tar.bz2";
      md5 = "a25cd6eb5e753703823fdd3ae86e9f25";
    };
  
  
  