CVSTrac includes a full-featured wiki document system. What's unique is the ability to use wiki markup virtually anywhere where text can be entered, including things like tickets and check-ins.
Wiki Documentation
Revisions
Each version of a CVSTrac wiki page is kept in the database. This means that the entire history of a page can be examined, differences identified, old changes resurrected, etc.
History
Clicking the History link on any wiki page will toggle on a list of all revisions of the page, including the datestamp and user who made the change. It's then possible to quickly view each version of the page. It's also possible to delete specific revisions of a page.
Wiki page revisions which have been deleted will, obviously, not be available in this list.
Diff
Clicking on the Diff link for any revision of a wiki page will show the changes between that revision and the previous revision.
Attachments
Arbitrary files can be attached to wiki pages by clicking on the Attach link and uploading files.
Attachments to a page can be reference by filename in {image:} markup sections, allowing images to be attached to pages and directly embedded in the page content.