anchor.diff:  { stdenv
   , lib
  -, fetchurl
  +, fetchFromGitHub
   , fetchpatch
   , makeWrapper
   , cmake
  
positive.code: let
  
    _llvm_9 = llvm_9.overrideAttrs (prev: {
      patches = (prev.patches or []) ++ [
        (fetchpatch {
          url = "https://github.com/root-project/root/commit/a9c961cf4613ff1f0ea50f188e4a4b0eb749b17d.diff";
          stripLen = 3;
  
negative.code: 
  stdenv.mkDerivation rec {
    pname = "root";
    version = "6.26.08";
  
    src = fetchFromGitHub {
      owner = "root-project";
      repo = "root";
      rev = "v${builtins.replaceStrings [ "." ] [ "-" ] version}";
      sha256 = "sha256-cNd1GvEbO/a+WdDe8EHYGmdlw3TrOT2fWaSk+s7fw7U=";
    };
  
    nativeBuildInputs = [ makeWrapper cmake pkg-config git ];
  