bug#58525: 28.1: `vc-dir' (key sequence: C-x v d) fails when used with a CVS repository

[Eli Zaretskii <eliz@gnu.org>]

> Date: Fri, 14 Oct 2022 17:36:38 +0000 (UTC)
> From:  Mark Harig via "Bug reports for GNU Emacs,
>  the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>
> 
> 
> When attempting to retrieve a VC status for a directory or file
> when the VC backend is CVS, the `vc-dir' command fails with an
> error message.

I'm not sure I understand the reason for this elaborate setup.  It
sounds like CVSROOT is in ~/tmp1, but you expect Emacs to understand
that ~/tmp3/project1, which is outside of the ~/tmp1 tree, is part of
the CVS repository in ~/tmp1?  Why is the correct expectation?

FWIW, "C-x v d" in a CVS repository (i.e. a directory which has a
'CVS' subdirectory) does not signal an error, and displays the correct
VC status of the files.

> So, the code for `vc-dir' (or, key sequence C-x v d) contains an
> error in which it cannot correctly identify the VC backend if it
> is not provided, when the VC backend is CVS.

Please tell how Emacs was supposed to realize that ~/tmp3/project1
directory is a CVS repository.

Thanks.