Eli Zaretskii <eliz@gnu.org> writes:

>> Please add a warning along these lines:
>> 
>> (message "The `%s' command is obsolete since version %s, use `%s' instead"
>>          obsolete-name version current-name)
>
> Where and when will this warning be displayed?

I was thinking of something along the lines of the below patch.

Best regards,
Stefan Kangas