anchor.diff:  
   let
   
  +  version = builtins.readFile ./.version;
     versionSuffix = "pre${toString nixosSrc.rev}-${toString nixpkgs.rev}";
   
   
  
positive.code: 
      in
        # Declare the ISO as a build product so that it shows up in Hydra.
        runCommand "nixos-iso-${version}"
          { meta = {
              description = "NixOS installation CD (${description}) - ISO image for ${system}";
              maintainers = map (x: lib.getAttr x lib.maintainers) maintainers;
  
negative.code: 
      let
  
        versionModule =
          { system.nixosVersion = version + (lib.optionalString (!officialRelease) versionSuffix);
            isoImage.isoBaseName = "nixos-${type}";
          };
  
  