If you use duplicity with ftp- or ftps-backend you'll need to emerge ncftp or lftp as dependency. Adding dependencies via useflag seems to be a suitable way to do this...
Created attachment 287229 [details, diff]
Created attachment 287231 [details, diff]
allow lftp with ssl or gnutls useflag
Created attachment 287235 [details, diff]
wrong dependency (net-ftp/ncftp instead of net-lftp/ncftp) fixed
We don't normally add use flags for optional run time functionality that is not controlled at build time.
As Mike said, no need to add this, it's only runtime behaviour and nothing we need at compile time.
What about s3? Should it be removed?