a partial git-svn checkout

I'm trying to make git-svn only grab a couple of top-level directories from the svn repository. I can only see how to grab the entire repository, or a single subdirectory. Is this possible? How?

A little more background info:
At work we have a giant repository. A full checkout is about 8GB,
because it contains several projects and some cruft. So nobody makes a
full checkout. Specifically, there are 3 kinds of directories in
trunk/
1. development directories, which I personally do work on
2. library directories, which I need to build but don't actually work on
3. irrelevant directories, which I never need

Right now I just manually checked out all of 1, made symlinks for 2, and added that to git. That's a workable checkout size. However, I'm finding myself writing some scripts to deal with that, and I keep thinking: git-svn already does this (and better), except that I don't know how to tell it which directories to grab.

I don't really care about correctly importing tags and branches from svn, although it would be a nice bonus. Is there a good solution for this scenario already?

Tim