In Trac, req.args['payload'] is a JSON string. Here's an example
(indented for readability).

{
  "forced": false,
  "compare": "https://github.com/<user>/<project>/compare/<chgset>...<chgset>",
  "pusher": {
    "name": "<pusher_name>"
  },
  "repository": {
    "fork": false,
    "has_wiki": false,
    "name": "<project>",
    "language": "Python",
    "has_downloads": true,
    "url": "https://github.com/<user>/<project>",
    "created_at": "<datetime>",
    "description": "<description>",
    "private": false,
    "pushed_at": "<datetime>",
    "owner": {
      "name": "<name>",
      "email": "<email>"
    },
    "watchers": <int>,
    "organization": "<name>",
    "open_issues": <int>,
    "has_issues": false,
    "forks": <int>,
    "homepage": "<url>",
    "size": <int>
  },
  "head_commit": {
    "committer": {
      "username": "<username>",
      "name": "<name>",
      "email": "<email>"
    },
    "added": [],
    "author": {
      "username": "<username>",
      "name": "<name>",
      "email": "<email>"
    },
    "url": "https://github.com/<user>/<project>/commit/<changeset>",
    "timestamp": "<iso datetime>",
    "modified": [
      "<path1>",
      "<path2>",
      "..."
    ],
    "distinct": true,
    "message": "<commit message>",
    "removed": [],
    "id": "<changeset>"
  },
  "deleted": false,
  "commits": [
    {
      "committer": {
        "username": "<username>",
        "name": "<name>",
        "email": "<email>"
      },
      "added": [],
      "author": {
        "username": "<username>",
        "name": "<name>",
        "email": "<email>"
      },
      "url": "https://github.com/<user>/<project>/commit/<changeset>",
      "timestamp": "<iso datetime>",
      "modified": [
        "<path1>",
        "<path2>",
        "..."
      ],
      "distinct": true,
      "message": "<commit message>",
      "removed": [],
      "id": "<changeset>"
    }
  ],
  "after": "<changeset>",
  "created": false,
  "ref": "refs/heads/master",
  "before": "<changeset>"
}

Add an example of GitHub's payload.
Add an example of GitHub's payload.
