documentation, work in progress

docs/config-github.md

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+## GitHub
+
+GitHub's OAuth integration only allows us to specify a single callback URL. This means that if you are running a wiki farm with multiple DNS roots, you will need to configure a separate application with GitHub for each wiki domain.
+
+### Register an application with GitHub
+
+* Log into GitHub
+* Visit the Developer applications tab under OAuth applications in your Personal settings.
+* Click [Register New Application](https://github.com/settings/applications/new). The *new OAuth application* configuration screen is displayed:
+
+![GitHub New OAuth Application](./images/github-new-app.png)
+
+#### Set Application name
+
+* Enter a name related to your wiki server.
+
+#### Set Homepage URL
+
+* Enter the URL of a page that describes your wiki server.
+
+#### Set Authorization callback URL
+
+* Enter `https://example.wiki/auth/github/callback`, replacing `example.wiki` with your wiki server root domain.
+
+Note: If you are not ready to use HTTPS yet, you can use `http://example.wiki/auth/github/callback`
+
+Save your settings by clicking **Register application**. The new application's settings are shown:
+
+![GitHub Application Summary](./images/github-app-summary.png)
+
+This screen also allows you to adjust any settings, and add an logo.
+
+* Record the `Client ID` and `Client Secret` for use in configuring the wiki server.
+
+### Configure Wiki
+
+The wiki is configured by adding the `client ID` and `client secret` to the wiki domain part of the configuration.
+
+```JSON
+{
+  "farm": true,
+  "security_type": "passportjs",
+  "wikiDomains": {
+    "example.wiki": {
+      "github_clientID": "CLIENT ID",
+      "github_clientSecret": "CLIENT SECRET"
+    }
+  }
+}
+```