try to extract the repository name from the remote URL
push -u initial commit for GitHub::Create

If setting the origin to github was successful, check if there are any
commits (e.g. initial commit created by ::Git::Init) and if so, push the
current branch to the new repo with -u to set up tracking.

This allows immediately doing an edit/commit and a "dzil release" with
plugins that expect to be able to just do a "git push".