bug#67171: 30.0.50; (At least) some VC commands fail with project-prefix-or-any-command

[Juri Linkov]

>>> As an aside, it doesn't seem good that whether or not step four prompts
>>> you for a directory depends on whether the current buffer happens to be
>>> visiting a file or not.  Can we improve that, or is it inherent to the
>>> design of the new feature?
>> This was improved recently in bug#67145, so now you can set
>> 'vc-deduce-backend-nonvc-modes' to nil to avoid this prompt.
>> I'm not sure if nil should be the default value.
>
> I wonder if the "deduce in all modes" value should be t rather than nil.

Good idea since nil could be used to disable deduction completely.
Then maybe it should be defcustom?