> All this works fine with the patch below.  The only part of the patch
> that I don't like is too much code in the first part of vc-dir-mark-files
> that just resolves discrepancy between Dired and VC-Dir:
> dired-get-marked-files returns directory names without the trailing slash,
> but vc-dir-fileinfo->name returns directories with the trailing slash.

Ok, here's the patch that fixes these problems.

It moves that ugly piece of code to dired-vc-next-action
(see the comment "Fix deficiency of Dired by adding slash to dirs")

The problem is that dired-get-marked-files returns directory names
as they are displayed in the Dired buffer i.e. where directories are
without the trailing slash.

It's possible to append the trailing slash by adding the switch
"-p" to dired-listing-switches:

  ls -p, --indicator-style=slash append / indicator to directories

But Dired doesn't support trailing slashes because
dired-goto-file can't find directory lines with slashes.
Therefore the need for ugly code in dired-vc-next-action.

Anyway, this is the final version of this feature: