bug#66166: 30.0.50; [PATCH] Consider outline-heading-end-regexp in outline-font-lock-keywords

[Juri Linkov <juri@linkov.net>]

> Consider outline-heading-end-regexp in outline-font-lock-keywords.
>
> Example of use case:
> 1) emacs -Q
> 2) in *scratch* buffer, type ";;; Hello" in a new line, plus some line breaks
> 3) eval:
>    (setq-local outline-regexp ";;;*")
>    (setq-local outline-heading-end-regexp "\n")
>    (setq-local outline-minor-mode-highlight 'override)
>    (custom-set-faces '(outline-1 ((t :background "red" :extend t))))
>    (outline-minor-mode 1)
> 4) expected: since the outline-1 face has the extend attribute and the
> heading regexp ends in a line break, the outline-1 face on ";;; Hello"
> should be applied until the line break (extended)
>
> Patch:
> -                      (concat "^\\(?:" outline-regexp "\\).*"))
> +                      (concat "^\\(?:" outline-regexp "\\).*" outline-heading-end-regexp))

Thanks, your patch looks right.  I wonder if it might break something,
maybe need more testing.

Then it will fix the extend attribute only when outlines are expanded.
But when collapsed, changes in the display engine are required
to support the extend attribute over the ellipsis (bug#65896).