[Feature request] Remove write access in repos to stop students from pushing more codes

[PeterDaveHello]

I think assignment/homework usually has a deadline, thought we could checkout to commit before a datetime, but the commit log is easily to be faked, also sometimes student didn't configure the datetime and timezone on there machine, so I think so best way to make sure the code will be committed before deadline is to remove the write permission, which is not supported by teachers_pet currently, hope it can be added in, thanks!

[mikehelmick]

FYI - when I originally wrote this I would clone all the repositories to my local machine and then roll them back to the due date.

This allows you to have individual extensions for individual students easily.

[PeterDaveHello]

Yeah, I can easily fetch the remotes at deadline, but I just wonder if we could have this feature, 'cause we(teacher/ta/student) could make sure we have a common view on GitHub to make sure the status of assignment.