Juri,

I thought quite some bit on how we can add in a warning for key binding
change. But as Stefan says, it is probably not worth it.

First of, we would need to create a wrapper function or a wrapper macro to
create wrapper functions for all the commands that we want to phase out
from being bound with the "C-x w" prefix map. The wrapper function will
call the wrapped function and then issue a warning/message in the echo area
saying that that function is already bound to "M-s h" prefix and will no
longer be bound to "C-x w" prefix in future. After that, in a future emacs
version, the final step to unbind those "C-x w" bindings will remain.

On Thu, Jul 30, 2015 at 6:48 PM Stefan Monnier <monnier@iro.umontreal.ca>
wrote:

> > Do we have a 2-step deprecation process where the first step
> > is to warn the users about the planned changes by issuing
> > a message like “use the new key instead” like we do with
> > ‘define-obsolete-function-alias’ and ‘make-obsolete-variable’?
>
> No, for key-bindings we just make the change, since we don't pay nearly
> as much attention to breaking "user compatibility" (which can be fixed
> with a define-key in ~/.emacs).
> OTOH if the change ends up breaking third-party packages it might be
> more problematic.
>
>
>         Stefan
>