anchor.diff:  
   let
     stableVersion = "2.1.21";
  -  previewVersion = "2.2.0b4";
  +  previewVersion = "2.2.0rc3";
     addVersion = args:
       let version = if args.stable then stableVersion else previewVersion;
           branch = if args.stable then "stable" else "preview";
  
positive.code:   };
    guiPreview = mkGui {
      stable = false;
      sha256Hash = "03jlg4ncs69gv1dn1zsdm0ipvlg6r0lwf8myxric6vv4ks7qqd3w";
    };
  
    serverStable = mkServer {
  
negative.code:   };
    serverPreview = mkServer {
      stable = false;
      sha256Hash = "0a4gx0qhy50v7nivqn8c2kz07crgzg2105hzmwag8xw6bpqmgm1d";
    };
  }
  