bug#49731: 28.0.50; Filter xref results by filename

["Daniel Martín via Bug reports for GNU Emacs, the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>]

Dmitry Gutov <dgutov@yandex.ru> writes:

>
> But do we want it to be implemented using outline-mode? Because we
> want the corresponding visuals? Because otherwise a dedicated
> implementation shouldn't take much more code either (probably roughly
> the size of xref-truncation-width feature we added recently).
>

Yes, I think implementing the feature using outline-mode is not a good
idea.  It'll load a library that is not small, and more importantly, it
is confusing from a UI point of view: It's strange that the xref output,
which is initally non-foldable, becomes foldable when you want to filter
the output (one may think that why the output can't just be foldable by
default).

I'd like to take a spin at option 1). How do you think the filtering
should happen? At the xref backend level, or at the xref frontend level?
I think the filtering can happen in the frontend, provided that the
backend provides the necessary information (file path, and symbol type,
if we offer to filter by symbol type).

Is there any thread where this feature was discussed? Thanks.