bug#64575: 29.0.92; Help buffers are unnecessarily under Outline mode

[Juri Linkov <juri@linkov.net>]

>> OTOH, when some Help command will insert a heading line, then it will
>> be handled automatically.  For example, 'C-h m' (describe-mode) could
>> take advantage of outline-minor-mode with heading lines for every
>> displayed minor mode.
>
> If some Help feature can benefit from outline-minor-mode, it should
> turn that mode on by itself, not rely on that being set already by
> some other code.

I tried to enable outline-minor-mode in the output buffer of 'C-h m',
and it has some problems:

1. outline-regexp of 'C-h b' is not suitable for 'C-h m', because the
output of 'C-h b' is more uniform, but the output of 'C-h m' includes
free-form text that causes false positives for the regexp ".*:$".

2. heading lines of 'C-h m' are beginning with a link, so the link faces
are copied to the outline indicator.

Both these problems could be fixed by adding an asterisk to the beginning
of headings in 'C-h m', for example:

  * Font-Lock minor mode (no indicator):

Does this look nice?  Or should we try to find a regexp for existing output?

>> > The actual functions you use in "C-h f" don't matter; the point is
>> > that the Outline minor mode, once set by "C-h b", stays turned on in
>> > the *Help* buffers, instead of being reset when not needed.
>> 
>> If you still think it should be disabled everywhere outside of 'C-h b',
>> this could be fixed by such patch:
>
> Thanks, I think this should be installed on master (assuming that it
> solves the problem; I didn't have time to try it).

I did more testing, and pushed to master.