moving documentation to the repository

doc/setup-github.md

@@ -1 +1,49 @@
-github.md
+You may configure Drone to integrate with GitHub or GitHub enterprise. This can be configured in the `/etc/drone/drone.toml` configuration file:
+
+```ini
+[github]
+client = "c0aaff74c060ff4a950d"
+secret = "1ac1eae5ff1b490892f5546f837f306265032412"
+```
+
+### Environment Variables
+
+You may also configure GitHub using environment variables. This is useful when running Drone inside Docker containers, for example.
+
+```bash
+DRONE_GITHUB_CLIENT="c0aaff74c060ff4a950d"
+DRONE_GITHUB_SECRET="1ac1eae5ff1b490892f5546f837f306265032412"
+```
+
+### Github Enterprise
+
+You may also configure Drone to integrate with GitHub Enterprise. Note that if you are running GitHub Enterprise in private mode you should set `private_mode=true`, forcing Drone to clone public repositories with git+ssh.
+
+```ini
+[github_enterprise]
+url = "https://github.drone.io"
+api = "https://github.drone.io/api/v3/"
+client = "c0aaff74c060ff4a950d"
+secret = "1ac1eae5ff1b490892f5546f837f306265032412"
+private_mode = false
+```
+
+### User Registration
+
+User registration is closed by default and new accounts must be provisioned in the user interface. You may allow users to self-register with the following configuration flag:
+
+```ini
+[github]
+open = true
+```
+
+Please note this has security implications. This setting should only be enabled if you are running Drone behind a firewall.
+
+### Organization Whitelists
+
+When specified, only users belonging to these organization may login to the system. Use this option to enable self-registration while still limiting access to the general public.
+
+```ini
+[github]
+orgs = [ "drone", "docker" ]
+```