bug#33264: Whitelist vc-follow-symlinks as a safe file variable

[Gustavo Barros <gusbrs.2016@gmail.com>]

Hi all,

On Mon, Jul 15 2019, Lars Ingebrigtsen wrote:

> Dmitry Gutov <dgutov@yandex.ru> writes:
>
>> I've tried to imagine a security issue stemming from it (e.g. linking
>> to an external directory tree with its own dir-locals values, and
>> then... what?), but didn't really come up with anything significant.
>
> The doc string says that a nil is "dangerous", but doesn't say what the
> danger is:
>
> ---
> 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.
> ---
>
> I'm guessing it doesn't really mean "dangerous", but instead "not
> optimal in most cases".


I’ve been following this thread and, if I may chime in, I think a good
reference in this respect is to note that `find-file-visit-truename` is
marked as a safe-local-variable in "files.el".

(Except that, as far as I can tell, it doesn’t work as a local
variable. See https://emacs.stackexchange.com/q/51495/18951. But that is
beyond the point here.)

Best regards,
Gustavo Barros.