anchor.diff:  
   let
     stableVersion = "2.1.15";
  -  previewVersion = "2.2.0a2";
  +  previewVersion = "2.2.0a3";
     addVersion = args:
       let version = if args.stable then stableVersion else previewVersion;
           branch = if args.stable then "stable" else "preview";
  
positive.code:   };
    serverPreview = mkServer {
      stable = false;
      sha256Hash = "033bi1bcw5ss6g380qnam1qqyi4bz1cykbb3lparb8hryikicdb9";
    };
  }
  
negative.code:   };
    guiPreview = mkGui {
      stable = false;
      sha256Hash = "110mghkhanz92p8vfzyh4199mnihb24smxsc44a8v534ds6hww74";
    };
  
    serverStable = mkServer {
  