A submodule commit is a gitlink, special entry recorded in the index, created when you add a submodule to your repo;
It records the SHA1 currently referenced by the parent repo.
A git submodule update --init is enough to populate the laravel subdirectory in your repo.
Once it is filled, note that your submodule repo is in a detached HEAD mode.
As shown here, when switching branches in the parent repo, your submodule gitlink will change accordingly, but your submodule content won’t change until you make again a git submodule update (after the git checkout)