Port to EE: Include documentation about STAGING_ENABLED variable for AutoDevops

doc/topics/autodevops/index.md

@@ -498,6 +498,7 @@ also be customized, and you can easily use a [custom buildpack](#custom-buildpac
 | `BUILDPACK_URL`              | The buildpack's full URL. It can point to either Git repositories or a tarball URL. For Git repositories, it is possible to point to a specific `ref`, for example `https://github.com/heroku/heroku-buildpack-ruby.git#v142` |
 | `SAST_CONFIDENCE_LEVEL`      | The minimum confidence level of security issues you want to be reported; `1` for Low, `2` for Medium, `3` for High; defaults to `3`.|
 | `DEP_SCAN_DISABLE_REMOTE_CHECKS` | Whether remote Dependency Scanning checks are disabled; defaults to `"false"`. Set to `"true"` to disable checks that send data to GitLab central servers. [Read more about remote checks](https://gitlab.com/gitlab-org/security-products/dependency-scanning#remote-checks).|
+| `STAGING_ENABLED`            | From GitLab 10.8, this variable can be used to define a [deploy policy for staging and production environments](#deploy-policy-for-staging-and-production-environments). |
 
 TIP: **Tip:**
 Set up the replica variables using a
@@ -564,6 +565,22 @@ service:
   internalPort: 5000
 ```
 
+#### Deploy policy for staging and production environments
+
+> [Introduced](https://gitlab.com/gitlab-org/gitlab-ci-yml/merge_requests/160)
+in GitLab 10.8.
+
+The normal behavior of Auto DevOps is to use Continuous Deployment, pushing
+automatically to the `production` environment every time a new pipeline is run
+on the default branch. However, there are cases where you might want to use a
+staging environment and deploy to production manually. For this scenario, the
+`STAGING_ENABLED` environment variable was introduced.
+
+If `STAGING_ENABLED` is defined in your project (e.g., set `STAGING_ENABLED` to
+`1` as a secret variable), then the application will be automatically deployed
+to a `staging` environment, and a  `production_manual` job will be created for
+you when you're ready to manually deploy to production.
+
 ## Currently supported languages
 
 NOTE: **Note:**