bug#39360: Add :extend attribute to show-paren-mode expression face

[Eli Zaretskii]

> From: Clément Pit-Claudel <cpitclaudel@gmail.com>
> Date: Thu, 30 Jan 2020 16:08:50 -0500
> 
> I've attached a patch to add :extend the show-paren-mode face applied to 
> expressions.  Is that the right way to return to the previous behavior?

Thanks.

Please describe a use case where this problem shows up, I'm not sure I
understand it completely.  More accurately, I don't think I understand
why you think we must have the previous behavior with this face,
i.e. why the new behavior is "wrong".

> I might have missed discussions about this; is there a reason why :extend t 
> isn't the default?

Because the whole idea of introducing :extend was that almost all
faces don't need this attribute.