/**
* Finds the directory for this AU. If none found in the map, designates a new dir for it.
*
* @param au the AU
* @param repoRoot root of the repository
* @return the dir {@link String}
*/
static String getAuDir(ArchivalUnit au, String repoRoot, boolean create) {
return getAuDir(au.getAuId(), repoRoot, create);
}