Document stages and jobs.

docs/gitlab/drupal/index.md

@@ -10,7 +10,7 @@ tags:
 # GitLab CI for Drupal pipelines
 
 This project contains a number of pre-configured tasks for GitLab CI/CD that
-allow to run very powerful pipelines which contain the following stages:
+allow to run very powerful pipelines which contain the following stage order:
 
 - [.pre (predefined)](#pre)
 - [execute](#execute)
@@ -466,6 +466,34 @@ Rules, when the job should run:
 
 ### Postprocess
 
+#### Check 4 Updates Commit
+
+We start a docker image for php with the specifies versions:
+
+- `PHP_MAJOR_VERSION`
+- `PHP_MINOR_VERSION`
+
+The following jobs must run before successfully. Some are optional, which means, if they exist, this job waits for them
+to complete:
+
+- [Check 4 Updates](#check-4-updates)
+    - uses its artefacts
+- [Check 4 Security Vulnerability Advisories](#check-4-security-vulnerability-advisories)
+    - optional
+- [Check 4 Outdated Packages](#check-4-outdated-packages)
+    - optional
+
+First we have to do some preparation. This is done in the `before_script` section.
+
+- [.prepareaccess](#prepareaccess)
+- [.preparecomposerplugins](#preparecomposerplugins)
+
+
+
+Rules, when the job should run:
+
+- `$CHECKUPDATES` is set
+- we are on the `develop` branch
 
 ### Test