MetadataResolver metadataResolver = repositorySession.getResolver();
namespacesToCollapse = new LinkedHashSet<String>();
for ( String repoId : selectedRepos )
{
namespacesToCollapse.addAll( metadataResolver.resolveRootNamespaces( repositorySession, repoId ) );
}
for ( String n : namespacesToCollapse )
{
// TODO: check performance of this
namespaces.add( collapseNamespaces( repositorySession, metadataResolver, selectedRepos, n ) );