Added some setup instructions

source/ci_source/providers/Concourse.ts

@@ -5,6 +5,29 @@ import { ensureEnvKeysExist, ensureEnvKeysAreInt } from "../ci_source_helpers"
  * Concourse CI Integration
  *
  * https://concourse-ci.org/
+ *
+ *  ### CI Setup
+ *
+ *  With Concourse, you run the docker images yourself, so you will want to add `yarn danger ci` within one of your build jobs.
+ *
+ *   ``` shell
+ *    build:
+ *      image: golang
+ *        commands:
+ *          - ...
+ *          - yarn danger ci
+ *   ```
+ *
+ *  ### Environment Variable Setup
+ *
+ *  As this is self-hosted, you will need to add the `CONCOURSE` environment variable `export CONCOURSE=true` to your build environment,
+ *  as well as setting environment variables for `PULL_REQUEST_ID` and `REPO_SLUG`. Assuming you are using the github pull request resource
+ *  https://github.com/jtarchie/github-pullrequest-resource the id of the PR can be accessed from `git config --get pullrequest.id`.
+ *
+ *  ### Token Setup
+ *
+ *  Once again as this is self-hosted, you will need to add `DANGER_GITHUB_API_TOKEN` environment variable to the build environment.
+ *  The suggested method of storing the token is within the vault - https://concourse-ci.org/creds.html
  */
 export class Concourse implements CISource {
   constructor(private readonly env: Env) {}