Currrently run RBTools in snapshot view will get error message saying "To generate diff using parent branch or by passing revision ranges, you must use a dynamic view.

So I made some change to support snapshot view post-review, as it will be useful for clearcase users working on snapshot views.

As new to Python, I think the ugly code I changed could be improved. Anyway, it works.

The idea is to use 'cleartool get -to dest-pname pname' command to copy the revision to temp dir and then run diff on temp old new files.

Tested on Clearcase 7.1.2 snapshot view, the diff could be uploaded just like dynamic view.