Only run pages job on code/backstage/qa changes

Signed-off-by: Rémy Coutable <remy@rymai.me>

.gitlab/ci/pages.gitlab-ci.yml

@@ -2,6 +2,32 @@
 .if-canonical-dot-com-gitlab-org-group-master-refs: &if-canonical-dot-com-gitlab-org-group-master-refs
   if: '$CI_SERVER_HOST == "gitlab.com" && $CI_PROJECT_NAMESPACE == "gitlab-org" && $CI_COMMIT_REF_NAME == "master"'
 
+# Make sure to update all the similar patterns in other CI config files if you modify these patterns
+.code-backstage-qa-patterns: &code-backstage-qa-patterns
+  - ".gitlab/ci/**/*"
+  - ".{eslintignore,gitattributes,nvmrc,prettierrc,stylelintrc,yamllint}"
+  - ".{codeclimate,eslintrc,gitlab-ci,haml-lint,haml-lint_todo,rubocop,rubocop_todo,scss-lint}.yml"
+  - ".csscomb.json"
+  - "Dockerfile.assets"
+  - "*_VERSION"
+  - "Gemfile{,.lock}"
+  - "Rakefile"
+  - "{babel.config,jest.config}.js"
+  - "config.ru"
+  - "{package.json,yarn.lock}"
+  - "{,ee/}{app,bin,config,db,haml_lint,lib,locale,public,scripts,symbol,vendor}/**/*"
+  - "doc/api/graphql/reference/*" # Files in this folder are auto-generated
+  # Backstage changes
+  - "Dangerfile"
+  - "danger/**/*"
+  - "{,ee/}fixtures/**/*"
+  - "{,ee/}rubocop/**/*"
+  - "{,ee/}spec/**/*"
+  - "doc/README.md"  # Some RSpec test rely on this file
+  # QA changes
+  - ".dockerignore"
+  - "qa/**/*"
+
 pages:
   extends:
     - .default-tags
@@ -9,6 +35,7 @@ pages:
     - .default-cache
   rules:
     - <<: *if-canonical-dot-com-gitlab-org-group-master-refs
+      changes: *code-backstage-qa-patterns
       when: on_success
   stage: pages
   dependencies: ["coverage", "karma", "gitlab:assets:compile pull-cache"]