Merge branch 'master' into update-todo-in-uiupdate-todo-in-ui

* master: (435 commits)
  Change occurrence of Sidekiq::Testing.inline!
  Fix order-dependent spec failure in appearance_spec.rb
  Put a failed example from appearance_spec in quarantine
  Cache PerformanceBar.allowed_user_ids list locally and in Redis
  Add Grafana to Admin > Monitoring menu when enabled
  Add changelog entry
  Add salesforce logo
  Move error_tracking_frontend specs to Jest
  Only save Peek session in Redis when Peek is enabled
  Migrate markdown header_spec.js to Jest
  Fix golint command in Go guide doc to be recursive
  Move images to their own dirs
  Gitlab -> GitLab
  Re-align CE and EE API docs
  Rename Release groups in issue_workflow.md
  Update api docs to finish aligning EE and CE docs
  Update locale.pot
  Update TODO: allow_collaboration column renaming
  Show upcoming status for releases
  Rebased and squashed commits
  ...

1 files changed, 18 insertions, 0 deletions

diff --git a/doc/development/database_debugging.md b/doc/development/database_debugging.md
index 68d33a9d8e0..de2c5b43411 100644
--- a/doc/development/database_debugging.md
+++ b/doc/development/database_debugging.md
@@ -85,3 +85,21 @@ eric             37709   0.0  0.0  2518640   7524 s006  S    Wed11AM   0:00.79 s
 $ kill 87304
 $ kill 37709
 ```
+
+### db:migrate `database version is too old to be migrated` error
+
+Users receive this error when `db:migrate` detects that the current schema version
+is older than the `MIN_SCHEMA_VERSION` defined in the `Gitlab::Database` library
+module.
+
+Over time we cleanup/combine old migrations in the codebase, so it is not always
+possible to migrate GitLab from every previous version.
+
+In some cases you may want to bypass this check. For example, if you were on a version
+of GitLab schema later than the `MIN_SCHEMA_VERSION`, and then rolled back the
+to an older migration, from before. In this case, in order to migrate forward again,
+you should set the `SKIP_SCHEMA_VERSION_CHECK` environment variable.
+
+```sh
+bundle exec rake db:migrate SKIP_SCHEMA_VERSION_CHECK=true
+```