Hi Eitan,
almost... I have only one the NAV Development Environment that can export (and import) objects as text. Depending on the license you have this works nicely (but not always).
Then there is NAVObjectSplitter (on mibuso) to split/join .txt-based object files. Combine this with FreeCommander, a few batch scripts, and a revision control system like SVN or Mercurial, and you have a pretty effective (or so) source control system. That's the setup I'm using. It requires quite some discipline, though.
with best regards
Jens