Commit messages should allow wiki syntax, and RecentChanges should format them
accordingly.

--[[JoshTriplett]]

That's a neat idea! It would probably have to be only the simpler bits,
without preprocessor directives -- wouldn't want a commit message inlining
a whole page into RecentChanges. Of course, it could only use _one_ of the
available markups, ie the default markdown. --[[Joey]]

To go along with this, the preview should show the formatted commit message.
--[[JoshTriplett]]