bug#60285: xref-query-replace-in-results could show an arrow pointing to the current item being replaced

[Dmitry Gutov]

On 23/12/2022 21:16, Daniel Martín via Bug reports for GNU Emacs, the 
Swiss army knife of text editors wrote:
> Severity: wishlist
>
> When you use xref-query-replace-in-results to replace some references,
> it'd be great if the xref buffer showed an overlay arrow (see
> xref--set-arrow) pointing to the reference being edited.  That'd give
> better context about the reference that is being edited and the global
> progress of the query replace operation.

SGTM.

Here's a patch which seems to work. It's a little tricky, though, and 
I'm at a loss with better variable names in some places.

Wish we had some unit tests here.

xref-replace-with-arrow.diff
Description: Text Data