That won't work with the import modules now, I'm not sure if it ever worked (even though the documentation says --path can be an rsync location). Download the ISO or rsync the files locally, and then point --path at that directory.
I can verify that this worked (cobbler import --path=rsync://...) as of February 2010. I'm sure I've done it since then but that's the last time I have an import documented.
From what I can tell, it looks like the old importer would rsync from
the given path to the local system and then determine the distribution's breed. This code is also present in version 2.2.1's ImportRedhatManager's run() method but I don't think it ever gets that far. check_for_signature() expects a local path and it's called in BootAPI's import_tree() method before run() is.
I think this functionality can be restored if import_tree() handles downloading trees from remote sources before calling check_for_signature() in the import modules.
Actually, this does work today. You just have to specify --breed on the command line since there are no local files to scan.
$ cobbler import --path=rsync://rsync.mirrorservice.org/download.fedora.redhat.com/pub/fedora/linux/releases/14/Fedora/x86_64/os/ --name=F14 --breed=redhat task started: 2011-10-15_012126_import task started (id=Media import, time=Sat Oct 15 01:21:26 2011) scanning rsync://rsync.mirrorservice.org/download.fedora.redhat.com/pub/fedora/linux/releases/14/Fedora/x86_64/os/ for a redhat-based distro signature Warning: No distro signature for kernel at rsync://rsync.mirrorservice.org/download.fedora.redhat.com/pub/fedora/linux/releases/14/Fedora/x86_64/os/, using value from command line running: rsync -a 'rsync://rsync.mirrorservice.org/download.fedora.redhat.com/pub/fedora/linux/releases/14/Fedora/x86_64/os/' /var/www/cobbler/ks_mirror/F14 --exclude-from=/etc/cobbler/rsync.exclude --progress ...
So, this at least is a work-around for now. Beyond that, we could just move all of that code from the individual import modules into import_tree() like you say. I actually like that idea anyway, because it removes a lot of code duplication - it just won't be a trivial change.