bug#33476: [PATCH] Fix occur revert with list-matching-lines-jump-to-current-line

[Juri Linkov <juri@linkov.net>]

>> > I reproduced this bug with Emacs 26.1 and 26.1.90 using -Q option.
>> >
>> > When pressing 'g' (revert-buffer) in an *Occur* buffer, in the case of
>> > having `list-matching-lines-jump-to-current-line' set to non-nil, the
>> > function errors as it can't find orig-line.
>> >
>> > I'm attaching a patch that adds a guard to the list of guards before
>> > inserting the current line.
>> 
>> Eli, is it ok to install this submitted patch to the release branch emacs-26?
>> At least, it prevents the error signal.
>> 
>> I see that for Emacs 27 in master this feature is completely rewritten.
>
> It was rewritten to fix the same bug, AFAIU, see bug#32543.  Why do we
> need to solve it again in emacs-26?

I guess porting the fix from master to emacs-26 is not safe.

> And which patch do you propose for the emacs-26 branch?

I propose to install the patch from OP.  This patch avoids the error.
It still might behave incorrectly in some cases, but at least it
doesn't raise the error.

>> But still I found a bug in master that can be fixed with another patch.
>> The following patch is for Emacs 27:
>
> What is the bug you found in the master branch?

In the master branch when `list-matching-lines-jump-to-current-line'
is non-nil, it doesn't show the current line highlighted.