How to write unit tests for GitPython clone/pull functions?

I have a python project that is using GitPython to perform clone and pull functions against a remote Git repository.

As a simple example:

import git
from git import Git
from git import Repo

def clone_and_checkout(self, full_dir, git_url, repo_ver):

    repo = Repo.clone_from(
        url=git_url,
        to_path=full_dir
    )

    # Set origin and pull
    origin = repo.remotes.origin
    origin.pull()

    # Check out desired version of repository
    g = Git(self.fulldir)
    g.checkout(repo_ver)

I want to be able to write a unit test for this function, but obviously this needs to reach out to an external system as it stands currently.

I am curious if anyone has experience mocking up this external interaction, in a manner similar to using Mock to mock up HTTP calls. I'd like to be able to perform these tasks in a way that can be mocked at test time without needing to call an actual Git remote.

How should I go about writing tests for this?