Repository Exists condition bugs

First, thanks a million for this module. I've been looking for something like this -- simple, and flexible without the overhead of the project module. This fits the bill perfectly. Anyway, just wanted to point out a couple of bugs in the "repository exists" condition. First, it takes 2 arguments, but only uses 1 (it seems like only one is really needed). Second, it doesn't actually check if the named folder is a git repository, only that the folder exists. The attached patch gets rid of the "Repository" argument for this condition and checks that the named folder exists and is a git repository (either bare or not bare).