bug#49731: 28.0.50; Filter xref results by filename

[Dmitry Gutov <dgutov@yandex.ru>]

On 27.07.2021 23:51, Juri Linkov wrote:

>> I think that kind of search scoping in advance can be specially useful
>> when you are doing a grep-like search in the codebase, using either
>> grep, rgrep, project-find-regexp, or xref-find-apropos.
> 
> Then in your comparison with grep, this is similar to grep options
> 'grep-find-ignored-directories' and 'grep-find-ignored-files'.

Except in reverse (inclusion, not exclusion) and tweakable at runtime 
rather that through Customize.

>> I didn't have in mind implementing cumulative filters.  I don't know if
>> people would need such advanced filtering of results.
> 
> Earlier you compared this to flush-lines/keep-lines, and these commands
> are cumulative.  But maybe xref filtering doesn't need to be cumulative
> when it will support specifying a regexp with alternatives '\|'.

I think ultimately it depends on the mental model the UI produces. In 
the examples we've seen in other programs, you usually modify an input 
field containing the previous search terms, so that makes it obvious the 
existing filter would be replaced, rather than added to.

If the new prompt did that as well, it could work similarly.