Installing a guix pull profile in VM and systems

[Julien Lepiller <julien@lepiller.eu>]

Hi Guix!

we get some perplexed users who are downgrading their VM and systems
because they never run guix pull. I think they now get a warning, but
it would be nice if they didn't get that warning in the first place.

For a VM for instance, a user might want to run it, and extend it with
"guix system reconfigure" to add some services. When doing that, the VM
uses the default guix package that is used to run the daemon, which is
at least one commit older than the guix that was used to build the VM.
So that guix has a different package set, and users start building
stuff, even when running something like "guix system reconfigure
/run/current-system/configuration.scm" which should not rebuild
anything.

Do you know how we could install the current guix profile to the VM, so
that it would be used instead of the default guix? That way both the
guix in the VM and outside would be on the same commit and we would not
have to rebuild anything in the VM.