partial checkouts

so I'm trying to convert KDE's translation helper scripts to support git repositories for kde modules. the translators themselves are staying in svn for now, but we want to start migrating kde modules over to git.

I've hit a bit of a problem, though. inside the translators' folder, there's a folder called documentation/ - and inside that is a bunch of svn externals pointing to the doc/ folder of every kde module. (this is, then, all of kde's english documentation.) translators occasionally need to run a script that reads from the documentation/ folder.

now, what happens when one of those modules switches to git? first, the svn external goes away. that's ok, I can work around that by having the update_xml script (the one translators need to run) fetch the doc folder itself, right? but where does it fetch it from? doc/ is now a subdirectory in a git repository, and git doesn't support checking out only one folder, not even if all I want to do is read the files in it.

checking out the entire git repo isn't really feasible, because once KDE finishes switching to git that'll mean checking out all of KDE. I don't think that turning every doc folder into a submodule is feasible, either - they sound kinda awkward to work with, and I can imagine lots of people getting confused and messing them up...

right now all I've thought of is one ugly hack: have a server that checks out all the kde git repos, pulls daily, copies all the doc/ folders into a documentation folder, and offers that folder up on the interwebs so that update_xml can rsync from it or download a tgz of it or something. there appear to be lots of images in the documentation, so it's not a small download - 200mb and growing. it still hasn't finished downloading all the externals...

I'm kinda wondering if there'd be a way to use git-filter-branch to make a repo that only tracks the doc/ folder for a module - but I've no idea whether it'd have to be recreated from scratch every time someone changes something in the real repo's doc/

can anyone think of a less ugly solution? what are the chances of git supporting this kind of partial checkout someday?