git submodule add https://github.com/koron0902/CocoaLib.git <path/to/submodule>
cd <path/to/submodule>
echo CocoaLib/chip > <repository_root>/.git/modules/<path/to/submodule>/info/sparse-checkout
echo CocoaLib/cocoa >> <repository_root>/.git/modules/<path/to/submodule>/info/sparse-checkout
git submodule update --recursive