bug#35222: 26.1; `read-command' documentation

[Noam Postavsky]

Stefan Monnier <monnier@IRO.UMontreal.CA> writes:

>>> 1. The doc string does not say what happens if DEFAULT is not provided
>>>    (so `nil') and the user enters empty input.  And what happens is not
>>>    obvious.  Please add that information to the doc string.
>> Um, can we declare the current behaviour a bug, and instead return nil
>> in this case? That matches the current doc string (i.e., return
>> DEFAULT-VALUE), and avoids the whole mess with the empty string symbol
>> which is weird and pretty useless as far as I can tell.
>
> Yes, it would seem to be more in line with the usual expected behavior.
> The caller can get the current behavior by passing ## as the DEFAULT
> argument, so there doesn't seem to be any good reason to return ## when
> DEFAULT was nil.

Since this bug is already closed, this should go Bug#35231.