bug#34949: 27.0.50; Docstring of `vc-deduce-fileset' incomplete

[Juri Linkov]

>> The user should have an overview of the fileset in VC-Dir before
>> committing it.  Thus I'm going to implement this design: when
>> a directory is marked in Dired, then invoking 'C-x v v' in Dired will
>> open the *vc-dir* buffer and mark the same directory in it.
>
> Fair enough. I think I preferred your other idea a bit more, but this also
> sounds workable.

I'd rather delegate the responsibility of handling all intricate details
of filesets to vc-dir-mode.

> Except... if a directory selected in a VC-Dir buffer contains files in
> "incompatible" states, vc-next-action should complain as well.

This is fine, vc-next-action called from the VC-Dir buffer
should do the right thing.