anchor.diff:  
   stdenv.mkDerivation rec {
     pname = "knot-dns";
  -  version = "2.9.6";
  +  version = "3.0.0";
   
     src = fetchurl {
       url = "https://secure.nic.cz/files/knot-dns/knot-${version}.tar.xz";
  -    sha256 = "bf742883c6825b54f19f2dadca2c94fec1ff8bdcf0a52388e2e167937594b2e7";
  +    sha256 = "f1c96aff6e873a2f9b1b8c2441d5a7801dd48d3abdb738a4d24b26c2a8fbe6c4";
     };
   
     outputs = [ "bin" "out" "dev" ];
  
positive.code:     gnutls liburcu libidn2 libunistring
      nettle libedit
      libiconv lmdb libintl
      libmaxminddb # optional for geoip module (it's tiny)
      # without sphinx &al. for developer documentation
    ]
      ++ optionals stdenv.isLinux [ libcap_ng systemd ]
      ++ optional stdenv.isDarwin zlib; # perhaps due to gnutls
  
negative.code: { stdenv, fetchurl, pkgconfig, gnutls, liburcu, lmdb, libcap_ng, libidn2, libunistring
  , systemd, nettle, libedit, zlib, libiconv, libintl, libmaxminddb, libbpf, nghttp2
  , autoreconfHook
  }:
  
  