anchor.diff:    };
     serverPreview = mkServer {
       stable = false;
  -    sha256Hash = "1bq4ww6qhhl0qw6yj7cf7yg54yb4y8mxlnwss6hgbyfv5fz9rxjp";
  +    sha256Hash = "0mzn62649hmmqq8z2vphqvi0w38jwq8ps4zzbl1dqygbf4gadnqa";
     };
   }
  
positive.code: 
  let
    stableVersion = "2.1.21";
    previewVersion = "2.2.0b3";
    addVersion = args:
      let version = if args.stable then stableVersion else previewVersion;
          branch = if args.stable then "stable" else "preview";
  
negative.code:   };
    guiPreview = mkGui {
      stable = false;
      sha256Hash = "03jlg4ncs69gv1dn1zsdm0ipvlg6r0lwf8myxric6vv4ks7qqd3w";
    };
  
    serverStable = mkServer {
  