bug#43464: 28.0.50; vc: Error calling vc-revert for repo root

[Andrii Kolomoiets]

Dmitry Gutov <dgutov@yandex.ru> writes:

> On 18.09.2020 18:45, Andrii Kolomoiets wrote:
>> BTW vc-revert is also works fine in Git repo when point is on
>> subdirectory.  So for the vc-git only reverting repo root is not
>> working.
>
> That's an interesting observation.

And the most interest part of that observation is that I can't reproduce
it :)

>> Please see attached patch which make it possible for vc-hg to revert
>> directory.
>
> Could you explain both changes in that patch?

The idea is to make the 'vc-backend' function to return backend for
directory.  'vc-backend' function uses the 'vc-registered' function.
The change for vc-hg.el makes 'vc-hg-registered' return t for directory.
The change to vc.el makes the 'vc-register' function called on directory
to not error with "already registered" message.

Chances that the patch is completely wrong.  Perhaps `vc-backend` should
return correct backend for directory and the behavior of `vc-registered`
must be kept unchanged.

> And also: how does it change, or not change, the behavior of vc-revert
> in backends that are not Git or Hg?

Looks like everybody is ready for reverting dirs.

bzr, mtn, svn - Should be fine reverting directory
dav - do nothing on vc-revert
rcs - reverting directory is added in c22b0a7da32360e34f6f0ff86a886c9028b3d863
sccs - reverting directory is added in e7290559824406d111d306069b36dde8ced847f9
src - reverting directory is supported initially 
1e81f6769013e1a0df9e10d7c5d0a3e3ca131143
cvs - passing directory to 'unedit' command should be fine