bug#61215: 29.0.60; font-lock broken in diff-mode with long lines

[Juri Linkov]

>> After debugging I discovered that the problem is not caused by font-lock
>> in diff-mode.  The problem is in easy-mmode-define-navigation.
>> diff-mode uses it to navigate diff hunks.  It supports such a feature
>> that when the user narrowed the diff buffer, it puts narrowing back
>> after moving to the next hunk.  But this fails when the diff buffer
>> is narrowed automatically by long-line-optimizations.  If there is
>> no way to distinguish whether the narrowing is automatic by long-lines
>> or manual by the user, this patch fixes the problem.  It works without
>> errors, and even highlights first 250000 characters of the long line:
>
> Thanks.
>
> Maybe Gregory (CC'ed) can help here and tell whether there's a better
> solution.

It seems there is no better solution?