bug#25061: consider adding %COMPAT to default gnutls priority string

[Ted Zlatanov <tzz@lifelogs.com>]

On Sun, 10 Dec 2017 09:04:30 +0200 Eli Zaretskii <eliz@gnu.org> wrote: 

EZ> Is everything you proposed strictly needed to fix the original
EZ> problem?  It sounds like a lot of changes just for having the
EZ> equivalent of '(setq gnutls-algorithm-priority "NORMAL:%DUMBFW")'
EZ> setting in effect.

It's a plan to provide a facility that can solve the underlying problem
of heterogeneous network setups.

EZ> E.g., could we simply make the above the default
EZ> value of gnutls-algorithm-priority for Emacs 26.1, and do all the rest
EZ> on master?

Yes, let's.

EZ> Previously, you said:

>> I'd rather stay with the current defaults and defer the rest of the work
>> to when connection-specific settings are available.

EZ> but you didn't explain why you didn't like changing the defaults.  If
EZ> that's because you thought it wasn't very clean, then would such a
EZ> change be okay just as a temporary measure, to be replaced by a
EZ> cleaner solution in Emacs 27?  Or can this default hurt something?

It would change behavior for everyone for the sake of fixing a few
setups. Does %DUMBFW or %COMPAT create a risk that's not justified by
the functionality it provides? These exceptions have a way of living
long past their expiration date.

If we're confident that's the right thing, then let's change it in the
release and add a note in the docs. I'm OK with the change; any other
comments? What should be the actual string?

Regardless, I'll make the connection profile changes in master, which
gives us more time to find problems and provide a better integration for
them. I'll discuss it in emacs-devel. Thank you for your consideration
and help.

Ted