code: public String getRootPath(CmsObject cms, String targetUri) {
  
          return getRootPath(cms, targetUri, null);
      }
docs: Returns the resource root path in the OpenCms VFS for the given target URI link, or <code>null</code> in
  case the link points to an external site.<p>
  
  This methods does not support relative target URI links, so the given URI must be an absolute link.<p>
  
  See {@link #getRootPath(CmsObject, String)} for a full explanation of this method.<p>
  
  @param cms the current users OpenCms context
  @param targetUri the target URI link
  
  @return the resource root path in the OpenCms VFS for the given target URI link, or <code>null</code> in
  case the link points to an external site
  
  @see #getRootPath(CmsObject, String, String)
  
  @since 7.0.2