My understanding is, you can't treat the filename as an arbitrary bytestring, since you have to transcode it across platforms, otherwise the filename won't show

My understanding is, you can't treat the filename as an arbitrary bytestring, since you have to transcode it across platforms, otherwise the filename won't show up properly everywhere. E.G. if I make a file named "test" on unix, it will be UTF-8 (assuming sane unix). If on windows I create a file with the filename "test", encoded as UTF-8, it will show up as worthless garbage in explorer.exe since it will decode it to UTF-16. So VCS needs to know the filename encoding in order to work properly.