What to do if visiting a symbolic link to a file under version control.
Editing such a file through the link bypasses the version control system,
which is dangerous and probably not what you want.
If this variable is t, VC follows the link and visits the real file,
telling you about it in the echo area. If it is `ask', VC asks for
confirmation whether it should follow the link. If nil, the link is
visited and a warning displayed.