anchor.diff:            Enable the periodic garbage collector.
           '';
         };
  -
   
         extraAttrs = mkOption {
           type = attrs;
  
positive.code:         '';
        };
  
        gc = mkOption {
          type = bool;
          default = true;
  
negative.code:   inherit (lib)
      concatStringsSep
      mkIf
      mkMerge
      mkOption
      optionals
      optionalAttrs;
  