anchor.diff:  
   , channel
   }:
  +
  +# NOTE: Tarballs hosted on bitbucket are non-deterministic.
   
   let
     inherit (stdenv)
  
positive.code:       }
      else
        fetchurl {
          url = "https://bitbucket.org/multicoreware/x265/downloads/"
            + "x265_${source.version}.tar.gz";
          inherit (source) multihash sha256;
        };
  
  
negative.code:   sources = {
      "stable" = {
        version = "3.0";
        md5confirm = "8ff1780246bb7ac8506239f6129c04ec";
        multihash = "QmTRoGtatifcPPHjL22njyYSn381wb6wJsrrDzZXtVMjm7";
        sha256 = "c5b9fc260cabbc4a81561a448f4ce9cad7218272b4011feabc3a6b751b2f0662";
      };
      "head" = {
  