A previous post has a comment from Jakub Narebski pointing me at git submodules. A quick google points me at: Andy Parkins' post on git submodules and svn:externals on kerneltrap.
That's cool. And if the anyone on my subversion using team ever uses svn:externals I'll be glad of the workaround. I hope, though, that git-svn support for svn:externals will mature before then :-).
I'm very happy with how flexible and powerful git is, and how I'm able to work on our svn repository while taking advantage of git capabilities that aren't in svn or are very painful to use. But I'm drowning quite well in java and erlang just now, and I'm not going to be able to spend time figuring out git nuances. Much better to sit around minding my own business while the product matures :-).