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

[Eli Zaretskii]

> From: Juri Linkov <juri@linkov.net>
> Date: Wed, 01 Feb 2023 20:18:09 +0200
> 
> >> when there is at least one long line near the end of
> >> a diff-mode buffer, then sometimes the buffer gets truncated,
> >> 'diff-hunk-file-names' returns nil on diff headings,
> >> and there are a lot of such errors in the Messages buffer:
> >>
> >>   Error during redisplay: (jit-lock-function 1) signaled 
> >> (args-out-of-range #<buffer *vc-diff*> 1118 1370)
> >
> > We can and should fix this and other problems, but only if they are
> > reported.  Would you please file a bug report for any such problem you
> > find?
> 
> This is a new bug report created from bug#56682.

Thanks.  Can you post a recipe for reproducing that, preferably
starting from "emacs -Q"?