Examine source code of Github PR Fetch

{
  "manifest_version": 2,
  "name": "Github PR Fetch",
  "version": "1.3",
  "description": "Display git fetch URL and ref name for a Github pull request",
  "icons": {
    "48": "icons/icon-48.png",
    "128": "icons/icon-128.png"
  },
  "permissions": [
    "activeTab",
    "https://github.com/*"
  ],
  "content_scripts": [
    {
      "matches": [
        "https://github.com/*/*/pull/*"
      ],
      "js": [
        "content.js"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{87c77e9d-ae76-4e8c-affe-bcd2eb99caaf}"
    }
  }
}