anchor.diff:  { nixpkgs ? { outPath = ./..; revCount = 5678; shortRev = "gfedcba"; }
   , officialRelease ? false
  +, stableBranch ? false
   }:
   
   let
   
     version = builtins.readFile ../.version;
  -  versionSuffix = "pre${toString nixpkgs.revCount}_${nixpkgs.shortRev}";
  +  versionSuffix =
  +    if officialRelease then ""
  +    else (if stableBranch then "." else "pre") + "${toString nixpkgs.revCount}.${nixpkgs.shortRev}";
   
     systems = [ "x86_64-linux" "i686-linux" ];
   
  
positive.code: 
  
    versionModule =
      { system.nixosVersionSuffix = pkgs.lib.optionalString (!officialRelease) versionSuffix;  };
  
  
    makeIso =
  
negative.code: 
        src = nixpkgs;
  
        officialRelease = false; # FIXME: fix this in makeSourceTarball
        inherit version versionSuffix;
  
        buildInputs = [ pkgs.nixUnstable ];
  
  