Github REST apis for tree , commit apis

Hello team ,

I was looking the Github API docs at this link here but unable to find any api for get_branch_for_repo, get_branch_for_repo, create_git_tree . Basically this is related to submodule updates and I need to create a webhook to update the the submodule’s latest commit SHA into the parent git repo.
But not able to find the apis. The same apis that have been used in the code mentioned in this link.

Please provide details on those apis.

Thanks