anchor.diff:  }:
   
   let
  -  version = "2020.3.11";
  +  version = "2020.3.12";
     shortVersion = builtins.substring 0 6 version;
     data = stdenv.mkDerivation rec {
       pname = "flightgear-data";
  
positive.code: 
      src = fetchurl {
        url = "mirror://sourceforge/flightgear/release-${shortVersion}/FlightGear-${version}-data.txz";
        sha256 = "sha256-Ej8VGywPQiDw3VXodcpXpOw4qU9x+MBMWMrqwHfitVg=";
      };
  
      dontUnpack = true;
  
negative.code: 
    src = fetchurl {
      url = "mirror://sourceforge/flightgear/release-${shortVersion}/${pname}-${version}.tar.bz2";
      sha256 = "sha256-wPeZIAiGU0zPBkzeBCO1xEgm+iZd/hWvBEr2ZcsX0Qc=";
    };
  
    # Of all the files in the source and data archives, there doesn't seem to be
  