Good point. For me, that was intentional, since all my projects are in git I don't care if it messes something up. Then you get the benefit of being able to use your regular git tooling/flows/whatever, without having to add credentials to the VM.

But if you need something more strict, 'config.vm.synced_folder' also supports 'type rsync', which will copy the source folder at startup to the VM, but then it's on you to sync it back or whatever.