bug#41974: 28.0.50; Some vc commands refuse to work when called on non-file buffer

[Juri Linkov]

> On 21.06.2020 02:55, Juri Linkov wrote:
>> I think this restriction should be lifted, so vc commands should
>> work even when called on non-file buffers whose default-directory
>> is inside the vc project.
>
> Agreed.
>
> Does this patch help, or does it miss more cases?
>
> diff --git a/lisp/vc/vc.el b/lisp/vc/vc.el
> index 9b12d44978..36013fcdc9 100644
> --- a/lisp/vc/vc.el
> +++ b/lisp/vc/vc.el
> @@ -2563,7 +2563,7 @@ vc-print-branch-log
>      (vc-read-revision "Branch to log: ")))
>    (when (equal branch "")
>      (error "No branch specified"))
> -  (let* ((backend (vc-responsible-backend default-directory))
> +  (let* ((backend (vc-deduce-backend))
>           (rootdir (vc-call-backend backend 'root default-directory)))
>      (vc-print-log-internal backend
>                             (list rootdir) branch t

Strange, this patch has no effect, the same error remains.