bug#33587: [PROPOSED] Default to disabling ImageMagick

[David Engster <david@engster.org>]

Glenn Morris writes:
> Note that Red Hat Enterprise Linux 8 _will_ drop ImageMagick completely
> (though it will probably be available from an add-on repository),
> presumably because they don't feel able to keep up with the security
> issues. That's what prompted me to first raise this in
>
> http://lists.gnu.org/r/emacs-devel/2018-12/msg00036.html

RHEL can do this because they're supporting way less packages than other
distributions. As you know, enterprise customers have other priorities
than home desktop users. Debian cannot remove Imagemagick because many
other packages depend on it, at least currently.

>> If for instance Debian has to take care of Imagemagick security issues
>> anyway, why shouldn't Emacs link to it?
>
> (For reference:
> https://security-tracker.debian.org/tracker/source-package/imagemagick )
>
> Because one can never guarantee all security issues are fixed, and if a
> project has a history of having a lot of them, it may be considered
> likely to be insecure. Also there are the various Emacs crash reports
> due to ImageMagick.

I understand the reasoning. To me, image scaling is essential for what
I'm doing with Emacs, so I'm willing to take that risk. But that's just
one data point.

Don't get me wrong: I don't object to disable it by default. Let's see
what happens. Maybe distributions will then disable it as well, but they
have their own ways to see how changes like these affect users (by
having an 'unstable' tree or whatever).

-David