bug#26969: 26.0.50; diff-changed invisible by default

[Lars Ingebrigtsen]

Stefan Monnier <monnier@IRO.UMontreal.CA> writes:

> Nowadays the `diff-changed` face is defined to be "invisible" (i.e. the
> text is displayed identically with or without that face).
> IOW it can only be used as a parent of diff-added or diff-removed (or
> some other such face).
>
> This is a bad idea since in cases such as vdiff.el where some changes
> are neither additions nor removals, it would make sense to highlight the
> buffer as just "changed" and using that face is a natural choice.
>
> I suggest the patch below for that.  It is designed such that it should
> make no visible difference to users of diff-added and diff-removed since
> these faces override the parts that are set by my patch in diff-changed.

That does sound a bit fragile...

> Another option would be to introduce a new face (not sure how to call
> it, maybe diff-unspecified-change, maybe?) which inherits from
> diff-changed as well.

I think that sounds more straightforward?

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no