bug#46859: 28.0.50; [PATCH]: Add option to truncate long lines in xref.el

[Gregory Heytings]

> > > But maybe your new option would be easier to customize.
> >
> > Yeah, maybe.  However, without benchmarking, it is quite clear that 
> > adding your option is faster than my patch, since ripgrep has to search 
> > the whole minified file.  I assume it short circuits, so that results 
> > are delivered quicker to emacs.  Maybe this bug can be closed.
>
> Your new option is still necessary for the default case when 
> 'xref-search-program' is 'grep' since GNU grep has no option to truncate 
> output, so xref should do post-processing for grep.

Actually, it is possible to truncate output with GNU grep:

grep -oE '.{0,100}PATTERN.{0,100}'

prints at most 100 characters before and after PATTERN.  I find this much 
better than ripgrep -M.