bug#37189: 25.4.1: vc-hg-ignore implementation is missing

[Wolfgang Scherer]

Am 23.02.20 um 16:20 schrieb Eli Zaretskii:
>> Cc: dgutov@yandex.ru, 37189@debbugs.gnu.org
>> From: Wolfgang Scherer <Wolfgang.Scherer@gmx.de>
>> Date: Sun, 23 Feb 2020 00:32:27 +0100
>>
>> What about the unwillingness of src status -a to recurse into
>> sub-directories, how does that correspond to Git, which can
>> often not be stopped to recurse?
> I was talking about this issue only from the POV of VC.  VC doesn't
> have to recurse, it can always run with default-directory set to the
> repository root, when SRC is the backend.

And how is the repository root defined?

What would the function vc-src-root look like?

How would vc-dir in a sub-directory of root learn about the files ignored?
default-directory is not the root in this case.