Eclipse: show SCCS diffs in overview ruler

I want Eclipse to show开发者_StackOverflow in the overview rules the diffs between what I have in memory (or on disk) and what's in ClearCase. I've set the preferences shown below, but it seems to be showing the diffs between what's in memory and what's on disk. In other words, every time I save, no diffs are shown. alt text http://img63.imageshack.us/img63/8937/eclipsew.png

Does this feature only work if using CVS for SCCS?

Update I'm using the unofficial ClearCase plugin, i.e. not the one developed by IBM

Thanks, Don

The diff you reference is only for the internal history, and is not linked to the official ClearCase IBM plugin for Eclipse.

The IBM plugin only calls an external diff tool, to show the difference between the last checked-in version and what is in your (snapshot or dynamic) view.