Splitting up a repository

Say I have a repo where there are directories repo/foo, repo/bar, repo/baz. 'foo', 'bar', and 'baz' are loosely related -- closely enough that I put them together initially, but loosely enough that I now wish I could check out just 'repo/foo'. Since Git doesn't support partial checkouts (a bit annoying!), I now have to split this repository into separate ones. I'd of course like to keep history.

Is there a better way than making several (recursive) copies of the repository, deleting all but one directory in each copy, then moving the contents of that directory up a level? (And perhaps setting up a Git superproject at the original location. I do know about that.)

I've probably spent more time typing up this email than it would take to do, but I'm curious if there's some git magic or something that would be better for some reason. :-)

Evan