When push commits to EMPTY project , there is no commit information in PUSH Webhook

The request body of PUSH Webhook is like:

{
  "object_kind": "push",
  "before": "0000000000000000000000000000000000000000",
  "after": "da1560886d4f094c3e6c9ef40349f7d38b5d27d7",
  "ref": "refs/heads/master",
  "user_id": 4,
  "user_name": "John Smith",
  "user_email": "john@example.com",
  "project_id": 15,
  "repository": {
    "name": "Diaspora",
    "url": "git@example.com:mike/diasporadiaspora.git",
    "description": "",
    "homepage": "http://example.com/mike/diaspora",
    "git_http_url":"http://example.com/mike/diaspora.git",
    "git_ssh_url":"git@example.com:mike/diaspora.git",
    "visibility_level":0
  },
  "commits": [],
  "total_commits_count": 0
}