This plugin adds an
add_underlays option to the setup file. Its value is
a list of underlay directories whose content is added to the wiki.
Multiple underlays are normally set up automatically by other plugins (for instance, the images used by the smiley plugin), but they can also be used as a way to pull in external files that you don't want in revision control, like photos or software releases.
add_underlays should usually be absolute. If relative,
they're interpreted as relative to the parent directory of the basewiki
underlay, which is probably not particularly useful in this context.