The command you mention does not work because vagrant has changed semantics and you need URL to install a box. If a box is downloaded you need file style like file:///d:/path/to/file.box
To make this repo universally usable (no matter into which directory it was cloned into) I had to use a relative path.
Any idea how to realize this with the new URL convention for config.vm.box?
The command you mention does not work because vagrant has changed semantics and you need URL to install a box. If a box is downloaded you need file style like file:///d:/path/to/file.box
vagrant box add my-box file:///d:/path/to/file.box