[Users] Feature request: Check repository urls in GetComponents

I just found that I had an old Kranc checkout from the wrong repository. Get Components did not notice this, and updated from this repository instead of aborting and/or switching to the new repository. (This explains why my version of Kranc didn't work.)

GetComponents should check this, and warn/abort if the checked out repository url is different from the one specified in the thorn list. I assume that people will move repositories from time to time for various reasons, and sticking with the wrong/old one should be noticed.

-erik