code: public void setExtendsDirectory(String extendsDirectory) {
          this.extendsDirectory = UrlUtils.cleanDirectory(extendsDirectory);
          if ("/".equals(this.extendsDirectory)) {
              this.extendsDirectory = null;
          }
          fileMethod.setExtendsDirectory(extendsDirectory);
      }
docs: httl.properties: extends.directory=layouts