mutation MergeGitHubPullRequest($input: MergeGitHubPullRequestInput!, $source: GitHubRequestSource!) {
  mergeGitHubPullRequest(input: $input, source: $source) {
    id
    state
    url
    mergedAt
  }
}

{
  "input": {
    "owner": "string",
    "name": "string",
    "number": 1,
    "method": "MERGE",
    "commitHeadline": "string",
    "commitBody": "string"
  },
  "source": "GITHUB_API"
}

{
  "data": {
    "mergeGitHubPullRequest": {
      "id": "id",
      "state": "string",
      "url": "string",
      "mergedAt": "string"
    }
  }
}