I wanted to create a new 'sub-repo' in the main hcmc repo for the SVG graphics I've been re-producing ('brand' grpahics and so forth), but I forgot how to add a sub-dir to an existing repo without checking out the parent - and I definitely didn't want to do that.
So here's how:
mkdir graphics
svn import graphics https://revision.hcmc.uvic.ca/svn/hcmc/graphics
Now I can populate the graphics dir and svn commit.