initial release

Support caching of github repos

git -c "http.http://github.saobby.my.eu.org.proxy=http://localhost:8080" \
    -c "http.http://github.saobby.my.eu.org.extraHeader=Authorization: token <github-oauth-token>" \
     clone http://github.com/my/private-repo.git