anchor.diff:      { splashImage = f config.boot.loader.grub.splashImage;
         grub = f grub;
         shell = "${pkgs.stdenv.shell}";
  -      fullVersion = (builtins.parseDrvName config.system.build.grub.name).version;
  -      inherit (config.boot.loader.grub)
  +      fullVersion = (builtins.parseDrvName realGrub.name).version;
  +      inherit (cfg)
           version extraConfig extraPerEntryConfig extraEntries
           extraEntriesBeforeNixOS extraPrepareConfig configurationLimit copyKernels timeout
           default devices;
  
positive.code:     # set at once.
      system.boot.loader.id = "grub";
  
      environment.systemPackages = mkIf config.boot.loader.grub.enable [ grub ];
  
    };
  
  
negative.code: 
        splashImage = mkOption {
          default =
            if cfg.version == 1
            then pkgs.fetchurl {
              url = http://www.gnome-look.org/CONTENT/content-files/36909-soft-tux.xpm.gz;
              sha256 = "14kqdx2lfqvh40h6fjjzqgff1mwk74dmbjvmqphi6azzra7z8d59";
  