anchor.diff:    };
     guiPreview = mkGui {
       stable = false;
  -    sha256Hash = "14fzjaanaxya97wrya2lybxz6qv72fk4ws8i92zvjz4jkvjdk9n3";
  +    sha256Hash = "0x4sp6yjnvzpk8cxdqlf51njckmvvkijdb7rvcb4hvqq1ab6gb2x";
     };
   
     serverStable = mkServer {
  
positive.code:   };
    serverPreview = mkServer {
      stable = false;
      sha256Hash = "03s2kq5f8whk14rhprg9yp3918641b1cwj6djcbjw8xpz0n3w022";
    };
  }
  
negative.code: 
  let
    stableVersion = "2.1.21";
    previewVersion = "2.2.0rc5";
    addVersion = args:
      let version = if args.stable then stableVersion else previewVersion;
          branch = if args.stable then "stable" else "preview";
  