docs: protected void findRoot(Collection<CmsResource> resources) throws CmsException {
  
          m_commonRoot = getCommonSite(resources);
          String commonPath = getCommonAncestorPath(resources);
          try {
              m_rootResource = m_cms.readResource(m_commonRoot, m_filter);
          } catch (CmsVfsResourceNotFoundException e) {
              String currentPath = commonPath;
              String lastWorkingPath = null;
              while (m_cms.existsResource(currentPath, m_filter)) {
                  lastWorkingPath = currentPath;
                  currentPath = CmsResource.getParentFolder(currentPath);
              }
              m_rootResource = m_cms.readResource(lastWorkingPath, m_filter);
              m_commonRoot = lastWorkingPath;
          }
          m_knownResources.add(m_rootResource);
      }