anchor.diff:  
   let
     channel = "2.9";
  -  version = "${channel}.3";
  +  version = "${channel}.4";
   in
   stdenv.mkDerivation rec {
     name = "nano-${version}";
  
positive.code:       "mirror://gnu/nano/${name}.tar.xz"
      ];
      hashOutput = false;
      sha256 = "7783bcfd4b2d5dc0bf64d4bd07b1a19e7ba3c91da881a4249772a36b972d4012";
    };
  
    nativeBuildInputs = [
  
negative.code:     srcVerification = fetchurl {
        failEarly = true;
        pgpsigUrls = map (n: "${n}.asc") src.urls;
        pgpKeyFingerprint = "BFD0 0906 1E53 5052 AD0D  F215 0D28 D4D2 A0AC E884";
        inherit (src) urls outputHash outputHashAlgo;
      };
    };
  