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

[Anders Lindgren]

Hi!

Eli:

I'm afraid that ship has sailed.  We need to find a solution to this
issue without going back.

I can agree with this.

The "xref" package is a big step forward, since it supports multiple backends etc. Unfortunately, vital functionality is missing -- searching and query-replace in all included files. Personally, I use `tags-search' at least 20 times per day (often more), and `tags-query-replace' several times each week. I don't think that my use pattern is extreme by any means.

I think that we would be making a big mistake if we would release Emacs 25 with an "xref" without searching and query-replace, but with key bindings that, for most tags users, break existing use patterns.

Dmitry:

> 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.

Today, many people use "tags" as a simple project file. They don't want to redo this process with another tool ("project") and a dired approach might not match a project layout at all.

Maybe I'm being naive, but a tags file (and presumably all other xref backends) must represent a list of files. A free text search and query-replace across those files would be very straight forward to specify, wouldn't it?

Eli:

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

It would have been neat... Unfortunately, the problem is not launching the command, but rather continue searching past the first match -- since a source buffer, and not the xref UI buffer, will be current.

I have given this some thought -- if we decide to really do make a change, maybe we should try to make the xref search command more isearch-like, so that a user could be able to continue an xref search using `C-s' rather than `M-,'. Unfortunately, there is no natural key binding to continue a normal query replace, but we could create something like `xref-query-replace-from-here', to continue query-replacing from the point in the current buffer and then continue with the next file in the file list.

   -- Anders