bug#44611: Prefix arg for xref-goto-xref

[Juri Linkov]

>> Maybe this is clearer: "kill the buffer that was current before popping 
>> back."
>
> Is that the XREF buffer?  Or is that the buffer where the definition
> was shown?

The latter.

> I don't understand why you call them "temporary": they are normal
> buffers visiting files that belong to the program you are working on,
> right?

These buffers are considered temporary only in one specific workflow:
when there is a need to quickly peek into a definition and immediately
jump back.

> And if you care so much about what goes into your desktop
> file, then you review the list of buffers each time before ending a
> session, right?

Alas, this is what required to do each time before ending a session.
Since it's a more general problem, I withdraw my patch that adds C-u
to kill the buffer.  It's too much hassle to type C-u before every 'M-,'.
There are too many commands that leave unwanted buffers.  For example,
browsing the grep results, visiting the next file doesn't kill the previous
visited file buffer, etc.  So better to clean up buffers afterwards,
using e.g. project-kill-buffers.