anchor.diff:  with stdenv.lib;
   
   let
  -  version = "20.0.2";
  +  # Release calendar: https://www.mesa3d.org/release-calendar.html
  +  # Release frequency: https://www.mesa3d.org/releasing.html#schedule
  +  version = "20.0.7"; # Update only to the final (last planned) release (i.e. X.Y.MAX)?
     branch  = versions.major version;
   in
   
  
positive.code:     changelog = "https://www.mesa3d.org/relnotes/${version}.html";
      license = licenses.mit; # X11 variant, in most files
      platforms = platforms.mesaPlatforms;
      maintainers = with maintainers; [ vcunat ];
    };
  }
  
negative.code: 
    src = fetchurl {
      urls = [
        "https://mesa.freedesktop.org/archive/mesa-${version}.tar.xz"
        "ftp://ftp.freedesktop.org/pub/mesa/mesa-${version}.tar.xz"
        "ftp://ftp.freedesktop.org/pub/mesa/${version}/mesa-${version}.tar.xz"
        "ftp://ftp.freedesktop.org/pub/mesa/older-versions/${branch}.x/${version}/mesa-${version}.tar.xz"
      ];
      sha256 = "0y517qpdg6v6dsdgzb365p03m30511sbyh8pq0mcvhvjwy7javpy";
    };
  
    prePatch = "patchShebangs .";
  