Do you mean for the initial set up, or in general?
If the former, it's possible, but finicky in some cases. There's an issue here, and it sounds like it's in the works:
If the latter, I think it's a matter of the scope of the package. usethis is intended to set up and structure workflows — it's not a full-blown git client (à la git2r or the newer gert package).
You could file a feature request if you feel like there's a compelling case for it.
Thanks Mara! I asked for the latter and I didn't want to use git2r. I thought usethis would already include it as it can be used to creae a project and the scope would be that of the project.
Thanks t your response, I now get to discover gert and I'm going to ask for the feature to see if it makes sense to have it inside usethis.