bug#23179: 25.0.92; Restore `M-,' to continue etags search

[Eli Zaretskii]

> Cc: 23179@debbugs.gnu.org
> From: Dmitry Gutov <dgutov@yandex.ru>
> Date: Sat, 2 Apr 2016 02:44:57 +0300
> 
> > I think the only viable solution is to provide a replacement for
> > tags-search that uses the xref UI to browse the results.
> 
> By now, we have both project-find-regexp and dired-do-find-regexp, which 
> provide different takes on the issue of "search through a set of files".

Depending on the specific use case (i.e. what is being looked for by
using tags-search), xref-find-references or xref-find-apropos or
xref-query-replace-in-results might also be relevant.

> If you want to have an xref-find-regexp as well, we should first 
> understand clearly how it would differ from those two commands. And its 
> specification cannot refer to tags files directly.

But we could have a tags-only command that presented an xref UI, I
think.  (Its name could be "tags-search" ;-)