bug#51016: 28.0.50; 'diff-font-lock-prettify' breaks display of outline headers

[Juri Linkov]

>> To circumvent this idiosyncrasy for headings in ‘describe-bindings’, I
>> had to use a different regexp in ‘outline-minor-mode-highlight-buffer’
>> (not based on font-lock):
>>
>>   (concat "^\\(?:" outline-regexp "\\).*$")))
>>
>> where ".+" is replaced with less-strict ".*".
>
> And diff-hunk-header-re definitely specifies an entire line.
>
> Perhaps we could just change the .+ thing to .* and see whether it
> breaks anything?

This looks like the right thing to do.  And this regexp in outline-mode

  (setq-local imenu-generic-expression
              (list (list nil (concat "^\\(?:" outline-regexp "\\).*$") 0)))

also uses .* instead of .+, probably because .+ caused a problem in imenu.