bug#81512: [PATCH] Add command `outline-occur'

 > It's fine for packages to add own rules to the existing value of
 > 'display-buffer-default-alist'.  Then the last package wins
 > when the first rule will match, e.g.:
 >
 >    (((category . bookmark-jump)
 >       display-buffer-for-package-2
 >       (package . 2))
 >     ((category . bookmark-jump)
 >       display-buffer-for-package-1
 >       (package . 1))

This means that once the user has loaded package-2, the behavior
prescribed by the previously loaded package-1 is lost.  This cannot
happen if package designers are told to let-bind that variable.

martin