Merge branch 'zj-test-migration-paths' into 'master'

Test migration paths

## What does this MR do?

It checks out the code base at v8.0.5, seeds the database, and runs all migrations. 

## Are there points in the code the reviewer needs to double check?

If this might make sense, does this simulate enough what happens in the real world.

## What are the relevant issue numbers?

Closes #14549 

## Does this MR meet the acceptance criteria?

- [x] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry added
- Tests
  - [x] Added for this feature/bug
  - [x] All builds are passing
- [x] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

See merge request !4874

.gitlab-ci.yml

@@ -248,6 +248,21 @@ bundler:audit:
   script:
     - "bundle exec bundle-audit check --update --ignore OSVDB-115941"
 
+migration paths:
+  stage: test
+  <<: *use-db
+  only:
+    - master@gitlab-org/gitlab-ce
+  script:
+    - git checkout HEAD .
+    - git fetch --tags
+    - git checkout v8.5.9
+    - 'echo test: unix:/var/opt/gitlab/redis/redis.socket > config/resque.yml'
+    - bundle install --without postgres production --jobs $(nproc) "${FLAGS[@]}" --retry=3
+    - rake db:drop db:create db:schema:load db:seed_fu
+    - git checkout $CI_BUILD_REF
+    - rake db:migrate
+
 coverage:
   stage: post-test
   services: []
@@ -263,7 +278,6 @@ coverage:
     - coverage/index.html
     - coverage/assets/
 
-
 # Notify slack in the end
 
 notify:slack:

CHANGELOG

@@ -24,6 +24,7 @@ v 8.12.0 (unreleased)
   - Add white background for no readme container (ClemMakesApps)
   - API: Expose issue confidentiality flag. (Robert Schilling)
   - Fix markdown anchor icon interaction (ClemMakesApps)
+  - Test migration paths from 8.5 until current release !4874
   - Optimistic locking for Issues and Merge Requests (title and description overriding prevention)
   - Add `wiki_page_events` to project hook APIs (Ben Boeckel)
   - Remove Gitorious import