anchor.diff:    { lib, stdenv, fetchpatch, perl, curl, bzip2, sqlite, openssl ? null, xz
     , bash, coreutils, gzip, gnutar
     , pkgconfig, boehmgc, perlPackages, libsodium, brotli, boost, editline, nlohmann_json
  -  , autoreconfHook, autoconf-archive, bison, flex, libxml2, libxslt, docbook5, docbook_xsl_ns
  +  , autoreconfHook, autoconf-archive, bison, flex
     , jq, libarchive
  +  , lowdown, mdbook
     # Used by tests
     , gmock
     , busybox-sandbox-shell
  
positive.code:           # This is not cross-compile safe, don't have time to fix right now
            # but noting for future travellers.
            nativeBuildInputs =
              [ perl pkgconfig curl nix libsodium boost autoreconfHook autoconf-archive ];
  
            configureFlags =
              [ "--with-dbi=${perlPackages.DBI}/${perl.libPrefix}"
  
negative.code: 
    nixUnstable = lib.lowPrio (callPackage common rec {
      name = "nix-3.0${suffix}";
      suffix = "pre20201020_e0ca98c";
  
      src = fetchFromGitHub {
        owner = "NixOS";
        repo = "nix";
        rev = "e0ca98c2071b815578470e280df8fdb750c7e23b";
        hash = "sha256-KVS/Z6FzMBOl5XCyOLwfiVoX7G2LQRa9HMGNnJRPCoo=";
      };
  
      inherit storeDir stateDir confDir boehmgc;
  