bug#6204: vc-dir always splits the frame

[Stefan Monnier <monnier@iro.umontreal.ca>]

>>> How would you proceed?
>> 1- fix all the Emacs code that modifies those vars.
> IMHO the only way to do that is to (1) provide a new set of variables
> Elisp code _is_ allowed to change and (2) have `display-buffer' use
> these iff the respective buffer has no corresponding entry in the
> special-display-... options.

Rather than let-binding some Lisp-manipulated "config" var, I was
thinking of passing special parameters to display-buffer (I'd rather
avoid dynamic scoping whenever possible).  Other than that, yes that's
the idea.

> If I do that and a buffer is now in the (same-window . t) group of
> `special-display-regexps', how should
> `Buffer-menu-switch-other-window' proceed with that buffer?
> Bind `special-display-regexps'?  Call `switch-to-buffer-other-window'?
> So far the special-display-... options had an excuse: If this variable
> appears \"not to work\", ...

You mean how could the calling code till display-buffer whether to
"prefer <foo> unless overridden by the user's config" or to "obey <foo>
regardless of the user's config"?
I guess the special parameters passed to display-buffer would have to be
different for the two different cases.


        Stefan