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

>> It's unlikely that two packages will use the same category.
>> Even in this case the user can change the order of package loading
>> the get the desired behavior for the same category.
>
> Suppose we provide a 'display-buffer' call for jumping to a bookmark in
> a canonical function 'bookmark-jump'.  Then that call would set
> 'category' to a symbol like 'bookmark-jump'.  Now if there are two
> different packages that call 'bookmark-jump' independently from each
> other and they both set 'display-buffer-default-alist' to a different
> value with category 'bookmark-jump', the result becomes unpredictable.
> Or am I missing something?

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))