git-svn: importing branches later

I've cloned the trunk of a SVN repository using git-svn and now I want
to bring in just a couple of the branches from the same repository.
I've not been able to discover anything that works.  Basically, I've
done this

$ git svn clone $URL -T trunk git-repo

Now I want to import the 'foo' branch from the same SVN repo without
grabbing all the branches.  Any suggestions?

Thanks.

-- 
Michael