anchor.diff:      the store using e.g.:
   
         releaseType=alpha
  -      version=0.16.51
  +      version=0.17.74
         nix-prefetch-url file://$HOME/Downloads/factorio_\''${releaseType}_x64_\''${version}.tar.xz --name factorio_\''${releaseType}_x64-\''${version}.tar.xz
   
       Note the ultimate "_" is replaced with "-" in the --name arg!
  
positive.code:   binDists = {
      x86_64-linux = let bdist = bdistForArch { inUrl = "linux64"; inTar = "x64"; }; in {
        alpha = {
          stable        = bdist { sha256 = "0b4hbpdcrh5hgip9q5dkmw22p66lcdhnr0kmb0w5dw6yi7fnxxh0"; version = "0.16.51"; withAuth = true; };
          experimental  = bdist { sha256 = "1q66chnxsdlaz1bj3al62iikyxvknj1vkwh5bcc46favy4wpqpzz"; version = "0.17.52"; withAuth = true; };
        };
        headless = {
          stable        = bdist { sha256 = "0zrnpg2js0ysvx9y50h3gajldk16mv02dvrwnkazh5kzr1d9zc3c"; version = "0.16.51"; };
          experimental  = bdist { sha256 = "03nv0qagv5pmqqbisf0hq6cb5rg2ih37lzkvcxihnnw72r78li94"; version = "0.17.52"; };
        };
        demo = {
          stable        = bdist { sha256 = "0zf61z8937yd8pyrjrqdjgd0rjl7snwrm3xw86vv7s7p835san6a"; version = "0.16.51"; };
        };
      };
      i686-linux = let bdist = bdistForArch { inUrl = "linux32"; inTar = "i386"; }; in {
  
negative.code: { stdenv, fetchurl, makeWrapper
  , alsaLib, libpulseaudio, libX11, libXcursor, libXinerama, libXrandr, libXi, libGL
  , factorio-utils
  , releaseType
  , mods ? []
  