anchor.diff:  
     };
   in
  -  combined
  +combined
  
positive.code:     let
        list =
          lib.concatMap
          (name:
            let v = set.${name}; in
            if pred name v then [v] else []
          )
          (lib.attrNames set)
          ;
      in
        if list == [] then default
        else lib.head list
        ;
  
    # The cryptpad package attribute key changes for each release. Get it out
    # programatically instead.
  
negative.code:     (k: v: v.packageName == "cryptpad")
      (throw "cryptpad not found")
      nodePackages
    ;
  
    combined = cryptpad.override {
      postInstall = ''
  