bug#34908: Push mark in xref-push-marker-stack

[Dmitry Gutov <dgutov@yandex.ru>]

On 19.03.2019 23:02, Juri Linkov wrote:

> Yes, its inconvenience is that you have to remember whether a previous
> position was in the same file or not, and depending on this decide
> what command to use: global or local pop.

Sooner or later, I believe we should rethink that UI.

>> Even so, I think it's been nice enough that every command can choose
>> whether it pushes the mark to the local/global buffer rights, and/or it
>> adds it to the xref marker stack. Do we have any particular guidelines in
>> the manual for when either should happen?
> 
> I think it should push to both.

OK.

> I'm not sure where to call push-mark: closer to the command,
> or closer to ring-insert.  It seems a suitable place for
> push-mark is in xref-push-marker-stack as its name suggests.

I'd rather have a more localized change, at least for now. And leave 
xref-push-marker-stack to only modify its own data structure.

So how about this?

diff --git a/lisp/progmodes/xref.el b/lisp/progmodes/xref.el
index 6974d00048..015ea16f34 100644
--- a/lisp/progmodes/xref.el
+++ b/lisp/progmodes/xref.el
@@ -797,6 +797,7 @@ xref--read-identifier-history
  (defvar xref--read-pattern-history nil)

  (defun xref--show-xrefs (xrefs display-action &optional always-show-list)
+  (push-mark nil t)
    (cond
     ((and (not (cdr xrefs)) (not always-show-list))
      (xref-push-marker-stack)