bug#33870: 27.0.50; xref-goto-xref not configurable

[Juri Linkov]

>>> 1. Make the current interface configurable
>>> 2. Present a number of configurations for xref to work
>>> with and how to select them.
>>
>> Of course, it should be configurable, I completely agree,
>> this is the whole point of this report.
>
> Then how about reviewing my patch?  It makes this configurable, and
> doesn't change the default configuration.
>
>> at this moment I have nothing more to say.
>
> Then if noone objects I'll push the patch I presented earlier in pa few
> days.  It makes xref-goto-xref configurable, doesn't change the default
> configuration, and closes this bug.

Making xref-goto-xref configurable is really important, this is the
raison d'être of this bug.  I wouldn't complain about configurable things.
For example, I'm not complaining that diff-hl-mode uses non-standard
blue color for changes whereas the standard diff-mode color is yellow.
Also I'm not complaining that flymake steals the fringe indicator from
diff-hl-mode, although there is no conflict because diff-hl-mode
uses the background color whereas flymake uses the foreground color,
so they can peacefully coexist together on the fringe.
Also I'm not complaining that often in ruby-mode C-M-f navigates to
unexpected places, however it's easy to fall back to M-f for more
predictable navigation, and so on.  But in case of xref-goto-xref
nothing helps.  This is why is this bug report.