anchor.diff:  
     nixUnstable = (lib.lowPrio (common rec {
       name = "nix-2.1${suffix}";
  -    suffix = "pre6338_45bcf541";
  +    suffix = "pre6377_954d1f4d";
       src = fetchFromGitHub {
         owner = "NixOS";
         repo = "nix";
  -      rev = "45bcf5416a0ce53361fd37c6b27ba4ef6a34ce96";
  -      sha256 = "0ps45n78wnczz99dd9fs54ydxwh2cjq73zbvmak0y49nhc3p0vvv";
  +      rev = "954d1f4d0a35063ff431b258beebadf753cb9efe";
  +      sha256 = "0wnljxljvcwmniydgxlsjqmbgghmljs75m6083y2nkjql7dnrm7g";
       };
       fromGit = true;
     })) // { perl-bindings = perl-bindings {
  
positive.code:       ++ lib.optionals is20 [ brotli ] # Since 1.12
        ++ lib.optional withLibseccomp libseccomp
        ++ lib.optional ((stdenv.isLinux || stdenv.isDarwin) && is20)
            (aws-sdk-cpp.override {
              apis = ["s3" "transfer"];
              customMemoryManagement = false;
            })
        ++ lib.optional fromGit boost;
  
      propagatedBuildInputs = [ boehmgc ];
  
negative.code: { lib, stdenv, fetchurl, fetchFromGitHub, fetchpatch, perl, curl, bzip2, sqlite, openssl ? null, xz
  , pkgconfig, boehmgc, perlPackages, libsodium, aws-sdk-cpp, brotli, boost
  , autoreconfHook, autoconf-archive, bison, flex, libxml2, libxslt, docbook5, docbook_xsl_ns
  , busybox-sandbox-shell
  