bug#10383: 24.0.91; (prefer-coding-system 'utf-8-with-signature) breaks the world

[Eli Zaretskii]

> From: Kenichi Handa <handa@m17n.org>
> Date: Wed, 28 Dec 2011 17:07:43 +0900
> Cc: 10383@debbugs.gnu.org
> 
> By the way, as a result, now
> 
>     (prefer-coding-system 'utf-8-with-signature)
> 
> does not change default-file-coding-system.  I'm not sure
> what is the intention of preferring utf-8-with-signature,
> one may want default-file-coding-system be set to utf-8 in
> such a case.  But, doing that automatically is too
> heuristic.

How about making prefer-coding-system display a message suggesting
that the user considers setting default-file-coding-system to utf-8?

> Another possibility is that what actually wanted is such a coding as
> utf-8-with-signature-on-decoding-only (i.e. on decoding, BOM is
> recognized, but on encoding, don't produce BOM).

If we can express this with current facilities, I'd say include that
information in the above-mentioned message.