Command line way to generate/update sidecar (xmp) files

Is there a command line way of updating the sidecar files to the latest version of darktable?

I can’t find anything in darktable-cli directly, so I’m wondering if perhaps there’s a way in a lua script to do that.

My current method is

darktable image.RAW oldSidecarFile.xml 

Then I simply duplicate the image under the duplicates manager.

Similarly, and possibly related, is there a way to create a default sidecar from an image from the command line? Currently simple open darktable with the raw file as the only parameter, and that creates the .xmp file. But running darktable-cli requires an xmp file as the second parameter, there doesn’t seem to be a way to simply say “used the defaults and create the xmp file, as if I’d opened this in the windowed version”.