anchor.diff:    };
     serverPreview = mkServer {
       stable = false;
  -    sha256Hash = "1jxkba7hc7271hjw3839r0yfzs87dzv1nqx62adhk9qrrcfqhg58";
  +    sha256Hash = "1a6ki0asai9x8xm724kha9phr2z8vkqfjwv067p860dpv2d2crxc";
     };
   }
  
positive.code:   };
    guiPreview = mkGui {
      stable = false;
      sha256Hash = "0kx68r8kgnsb7710a1a5y64blmw2jl1gv37bzbbivi15dzgmykfh";
    };
  
    serverStable = mkServer {
  
negative.code: 
  let
    stableVersion = "2.1.20";
    previewVersion = "2.2.0b2";
    addVersion = args:
      let version = if args.stable then stableVersion else previewVersion;
          branch = if args.stable then "stable" else "preview";
  