clone command accepts namespaced repostiory name, e.g. rpms/rpkg or modules/ant. But, it is optional and command help does not tell anything about this usage and what available namespaces could be used. This could confuse some new packagers.

--namespace option is used to provide an explicit way to specify namespace, which would make packagers happy. An example could be:

fedpkg clone --namespace modules ant

which is equivalent to

fedpkg clone modules/ant