bug#36967: 27.0.50; Duplicate lines in xref output

[Dmitry Gutov]

On 08.08.2019 0:52, Juri Linkov wrote:
> I tried to use project-find-regexp more often than rgrep,
> but unfortunately xref still has a fundamental flaw:
>
> 0. emacs -Q
> 1. M-x project-find-regexp RET regexp RET
> 2. The output buffer *xref* contains duplicate lines
>     when regexp is found on the same line several times,
>     each duplicate output line has separate highlighting
>     for every regexp occurrence.

I don't know how "fundamental" it is, but indeed, it's somewhat of a 
drawback. Suggestions for improving it (API change and/or implementation 
change) are welcome.