bug#34898: 24.4; `message-separator' face only works for default value of `mail-header-separator'

["Basil L. Contovounesios" <contovob@tcd.ie>]

[Sorry for the duplicate message Emanuel, I think your Mail-Followup-To
 and Mail-Copies-To headers caused my reply to be sent to the wrong
 place.]

Emanuel Berg <moasenwood@zoho.eu> writes:

> Eric Abrahamsen wrote:
>
>> The value of `mail-header-separator' gets
>> added to `message-font-lock-keywords', which
>> does the actual fontification. Using setq to
>> change the value of `mail-header-separator'
>> did not change the font lock keyword, despite
>> setting the variable before message.el is
>> loaded (or is it pre-loaded?). Using the
>> customize interface to set
>> `mail-header-separator' *does* work
>> as expected.
>>
>> Dunno if it's supposed to work this way
>> or not.
>
> All the other message faces don't behave like
> that but can be set as expected.
>
> Also the wierd behavior that it works with the
> default value for the `mail-header-separator'
> but not if one changes it.

The issue doesn't lie with the message-separator face, but with how
message-font-lock-keywords registers which text should be fontified with
that face.

Currently, message-font-lock-keywords registers only whatever non-empty
value mail-header-separator had at the time message.el was loaded.

-- 
Basil