anchor.diff:    };
     guiPreview = mkGui {
       stable = false;
  -    sha256Hash = "1lvdff4yfavfkjmdbhxqfxdd5nq77c2vyy2wnsdliwnmdh3fhm28";
  +    sha256Hash = "110mghkhanz92p8vfzyh4199mnihb24smxsc44a8v534ds6hww74";
     };
   
     serverStable = mkServer {
  
positive.code:   };
    serverPreview = mkServer {
      stable = false;
      sha256Hash = "033bi1bcw5ss6g380qnam1qqyi4bz1cykbb3lparb8hryikicdb9";
    };
  }
  
negative.code: 
  let
    stableVersion = "2.1.15";
    previewVersion = "2.2.0a3";
    addVersion = args:
      let version = if args.stable then stableVersion else previewVersion;
          branch = if args.stable then "stable" else "preview";
  