Nautilus supports TimeSlider ( via ZFS snapshots ) -> a comparison of different Versions of a file is possible

ZFS supports snapshots to store a version of the filesystem.
Tim Foster generated a package named zfs autosnapshots, which allows to
automatically make snapshots of the filesystem. In OpenSolaris this is
also available via a menu entry.

Since OpenSolaris 2009.06, nautilus has an additional feature.
In the dev-repository nautilus had for some releases the feature to open a slider
( TimeSlider ) to change the view of the version, when snapshots are available.
Now the context menu supports an entry named "Explore Versions".
This shows the available versions and if SUNWmeld is installed you can compare.

See a good entry in the blog of the The Observatory.