https://api.github.com/repos/:user/:repo/git/refs/heads/:branch_name

{
  "ref": "refs/heads/:branch_name",
  "node_id": ":something",
  "url": "https://api.github.com/repos/:user/:repo/git/refs/heads/:branch_name",
  "object": {
    "sha": ":commit_sha",
    "type": "commit",
    "url": "https://api.github.com/repos/:user/:repo/git/commits/:commit_sha"
  }
}
