@SuppressWarnings("unchecked")
  private ExternallyAddedFilesProcessorImpl createExternalFilesProcessor() {
    return new ExternallyAddedFilesProcessorImpl(myProject,
                                                 this,
                                                 myVcs,
                                                 (files) -> {
                                                   performAdding((Collection<VirtualFile>)files, emptyMap());
                                                   return Unit.INSTANCE;
                                                 });
  }
@SuppressWarnings("unchecked")
  private ExternallyAddedFilesProcessorImpl createExternalFilesProcessor()