This plugin allows you to configure ikiwiki with the location of rcs repositories for your wiki's source. This is done via the "repositories" setting in the setup file. Once you tell it where the source to your wiki can be downloaded from, this information can be published on your wiki in various ways.
This plugin supports the rel-vcs-* microformat, and uses it to embed the repository location information in every wiki page.
By using this plugin, you will make Joey very happy, as he will be able to easily check out the source of your wiki, for purposes of debugging and general curiosity. More generally, making it easy for others to find the repository for your wiki is just a Plain Good Idea(TM).