anchor.diff:  let
   
     mirror = https://get.geo.opera.com/pub/opera/desktop;
  -  version = "46.0.2597.39";
  +  version = "48.0.2685.52";
   
     rpath = stdenv.lib.makeLibraryPath [
   
  
positive.code:   meta = {
      homepage = http://www.opera.com;
      description = "Web browser";
      license = stdenv.lib.licenses.unfree;
    };
  }
  
negative.code: 
    name = "opera-${version}";
  
    src = fetchurl {
      url = "${mirror}/${version}/linux/opera-stable_${version}_amd64.deb";
      sha256 = "027njqh2as4d0xsnvzamqiplghb8cxqnc19y0vqkvjnsw57v828p";
    };
  
    unpackCmd = "${dpkg}/bin/dpkg-deb -x $curSrc .";
  
  