anchor.diff:      repo = "voms";
       rev = "8e99bb96baaf197f0f557836e2829084bb1bb00e"; # develop branch
       hash = "sha256-FG4fHO2lsQ3t/ZaKT9xY+xqdQHfdtzi5ULtxLhdPnss=";
  +  };
  +
  +  passthru = {
  +    inherit externalEtc;
     };
   
     nativeBuildInputs = [
  
positive.code: , gsoap
  , openssl
  , zlib
  }:
  
  stdenv.mkDerivation rec{
  
negative.code:     "--with-gsoap-wsdl2h=${gsoap}/bin/wsdl2h"
    ];
  
    postFixup = ''
      ${lib.optionalString (externalEtc != null) ''
        mv "$out"/etc{,.orig}
        ln -s ${lib.escapeShellArg externalEtc} "$out/etc"
      ''}
    '';
  
    meta = with lib; {
      description = "The C/C++ VOMS server, client and APIs v2.x";
      homepage = "https://italiangrid.github.io/voms/";
  