bug#54993: 28.1; Editing etc/NEWS on master with Emacs 28 signals an error

[Juri Linkov]

>> there are different outline header colors between Emacs 28 and 29
>> because of different outline levels.  The additional level comes
>> from the space character at the end of outline-regexp "^\\*+ ".
>
> I wanted to avoid having stuff like
>
> ** New thing for help buffers.
> *Help* buffers can be etc...
>
> triggering an outline thing on the second line.  Is there a way to do
> that without including the space in outline-regexp?

I see only 1 way: to set buffer-local outline-level where to subtract 1.