git-stats-importer also only imports commits by the user set in the global user.email config. Since you haven't made any commits to the git-stats repo, it doesn't show anything.
Edit: it will use the local user.email if that is set. It also will use the GIT_AUTHOR_EMAIL but only as a fallback if user.email is unset
Edit: it will use the local user.email if that is set. It also will use the GIT_AUTHOR_EMAIL but only as a fallback if user.email is unset