Re: New package `outline-occur'

> Using 'buffer-match-p' together with 'category' and 'this-command' has
> slowly defied any attempt to make a description of 'display-buffer' more
> amenable to both users and Elisp writers.  I would not be able to tell
> beforehand whether a 'this-command' or 'category' entry in "app-action"
> could affect whatever a user has specified in 'display-buffer-alist' and
> how.

Maybe we could simply allow an application to *append*
new rules to the end of 'display-buffer-alist',
thus not overriding the user customization?
For example:

(defun occur-outline (regexp &optional nlines region)
  (interactive (occur-read-primary-args))
  (let ((display-buffer-alist
         (append display-buffer-alist
                 `(((category . occur)
                    nil
                    (post-command-select-window . t))))))
    (occur-1 regexp nlines (list (current-buffer)))))