bug#6204: vc-dir always splits the frame

[martin rudalics]

>> `switch-to-buffer' is allowed to reuse a weakly dedicated window while
>> `display-buffer' isn't.
>
> Indeed, and that's on purpose.  It's basically that switch-to-buffer has
> a strong `same-window' parameter.  I don't think display-buffer and
> special-display-regexps have any way to specify such a request, so we'll
> need to add it.

Where "add it" means to include it as argument, I presume.  Doesn't this
mean we'd have to find a way to specify this in `special-display-regexps'
too?

martin