I am not advocating any sort of Zero Tolerance policy (e.g. "instantly failing") for this. In fact, I think ZT is insane in most if not all cases.

For the purposes of this discussion (which was about having students use version control for assignments) using version control is as central to the requirements as implementing the algorithm and using the assigned language and failure to follow instructions can, at the instructor's discretion, result in grading penalties. As a bonus, this adds another hurdle for cheaters to clear and provides another opportunity for profs/TAs to notice anything suspicious.

Hope that clears some things up...