anchor.diff:  # TODO: add assert statements
   
   let
  +  pkgs = import ./../../default.nix (if include-overlays then { } else { overlays = []; });
  +
  +  inherit (pkgs) lib;
  +
     /* Remove duplicate elements from the list based on some extracted value. O(n^2) complexity.
      */
     nubOn = f: list:
  
positive.code: 
    packageData = package: {
      name = package.name;
      pname = pkgs.lib.getName package;
      updateScript = map builtins.toString (pkgs.lib.toList package.updateScript);
    };
  
    packagesJson = pkgs.writeText "packages.json" (builtins.toJSON (map packageData packages));
  
    optionalArgs =
      pkgs.lib.optional (max-workers != null) "--max-workers=${max-workers}"
      ++ pkgs.lib.optional (keep-going == "true") "--keep-going";
  
    args = [ packagesJson ] ++ optionalArgs;
  
  
negative.code:   packagesWithUpdateScriptAndMaintainer = maintainer':
      let
        maintainer =
          if ! builtins.hasAttr maintainer' lib.maintainers then
            builtins.throw "Maintainer with name `${maintainer'} does not exist in `maintainers/maintainer-list.nix`."
          else
            builtins.getAttr maintainer' lib.maintainers;
      in
        packagesWith (name: pkg: builtins.hasAttr "updateScript" pkg &&
                                   (if builtins.hasAttr "maintainers" pkg.meta
  