Currently, there are no "client side hook scripts". So, what you are asking cannot be accomplished.
Also, what intrigues me is, any checkstyle scripts that you run have to be run on the "merged" code (i.e on the working copy, after the merge, before committing). So by this time, any necessary conflict resolution should have been done. So I don't see why you can't do this check at commit time anyway. If there are any inconsistencies, you can make the hook script return the errors from the checkstyle script, and all the user has to do now is to make the necessary changes and then try committing again. In fact, in my day job, we run these scripts manually before committing, so it saves a round trip to the server. Regards, Arwin Arni