[galaxy-user] Import files from filesystem path : No redundance?

Hi all, I have used the option "Import files from filesystem path" to import a complete arborescence of directories and files in one Data Library of Galaxy. Lot of files and sub-directories wil add to this arborescence. I've hoped import those changes in my data library with the option : add datasets, then indicate the path of this arborescence at the option "import from filesystem path". But when I use this way, Galaxy re-import all arborescence : the new files and sub-directories AND all already imported directories and files! Is there a way to import just the new files without know a priori which are new in my arborescence?* *Thanks. Julie* *