anchor.diff:        kind: GitHubIdentityProvider
         clientID: ... <5>
         clientSecret: ... <6>
  +      organizations: <7>
  +      - myorganization1
  +      - myorganization2
   ----
   <1> This provider name is prefixed to the GitHub numeric user ID to form an
   identity name. It is also used to build the callback URL.
  
positive.code: application]. The application must be configured with a callback URL of
  `<master>/oauth2callback/<identityProviderName>`.
  <6> The client secret issued by GitHub.
  ====
  
  [[Google]]
  
negative.code: `<master>/oauth/token/request` to use with command-line tools.
  ====
  
  [WARNING]
  ====
  Using GitHub as an identity provider allows any GitHub user to authenticate to your server.
  You can limit authentication to members of specific GitHub organizations with the
  `organizations` config attribute, as shown below.
  ====
  
  .Master Configuration Using *GitHubIdentityProvider*
  ====
  
  