code: public void addImmutableResource(String immutableResource) {
  
          if (LOG.isDebugEnabled()) {
              LOG.debug(
                  Messages.get().getBundle().key(
                      Messages.LOG_IMPORTEXPORT_ADDED_IMMUTABLE_RESOURCE_1,
                      immutableResource));
          }
          m_immutableResources.add(immutableResource);
      }
docs: Adds a resource to the list of immutable resources that should remain
  unchanged when resources are imported.<p>
  
  @param immutableResource a resources uri in the OpenCms VFS