stages maybe

rails/gitlab-ci.yml

+stages:
+  - detect_ruby
+  - test
+
 default:
   tags:
     - rails
@@ -7,44 +11,42 @@ default:
     - wget --quiet "https://git-ce.rwth-aachen.de/noc-public/noc-netze-gitlab-cicd/-/raw/main/rails/haml-lint.yml" -O ".haml-lint.yml"
     - rm -f ./config/brakeman.yml ./config/brakeman.ignore
     - gem install bundler --silent && bundle install --quiet
-    - export RUBY_VERSION=$(cat .ruby-version | sed 's/ruby-//g')
 
 variables:
   RAILS_ENV: test
 
+detect_ruby:
+  detect:
+    script: echo "RUBY_VERSION=$(cat .ruby-version | sed 's/ruby-//g')" >> ruby.env
+    artifacts:
+      reports:
+        dotenv: ruby.env
+
+test:
+  default:
+    image: ruby:$RUBY_VERSION
+
   rubocop:
-  stage: test
-  image: ruby:$(cat .ruby-version | sed 's/ruby-//g')
     script:
       - rubocop
 
   erb_lint:
-  stage: test
-  image: ruby:$(cat .ruby-version | sed 's/ruby-//g')
     script:
       - erblint --lint-all --allow-no-files true
 
   haml_lint:
-  stage: test
-  image: ruby:$(cat .ruby-version | sed 's/ruby-//g')
     script:
       - haml-lint
 
   brakeman:
-  stage: test
-  image: ruby:$(cat .ruby-version | sed 's/ruby-//g')
     script:
       - brakeman -A --except UnscopedFind
 
   rails_test:
-  stage: test
-  image: ruby:$(cat .ruby-version | sed 's/ruby-//g')
     script:
       - bin/rails db:prepare test
 
   rails_system_test:
-  stage: test
-  image: ruby:$(cat .ruby-version | sed 's/ruby-//g')
     services:
       - selenium/standalone-chrome:latest
     variables: