anchor.diff:        default = throw "You must specify `uploadDir'.";
         example = "/data/mediawiki-upload";
         description = "The directory that stores uploaded files.";
  +    };
  +
  +    defaultSkin = mkOption {
  +      default = "standard";
  +      example = "nostalgia";
  +      description = "Default skin: you can change the default skin.";
       };
   
       extraConfig = mkOption {
  
positive.code: with pkgs.lib;
  
  let
  
    mediawikiConfig = pkgs.writeText "LocalSettings.php"
      ''
  
negative.code:           $wgUploadDirectory = "${config.uploadDir}";
          ''}
  
          ${optionalString (config.defaultSkin != "") ''
            $wgDefaultSkin = "${config.defaultSkin}";
          ''}
  
          ${config.extraConfig}
        ?>
      '';
  