Merge branch 'reviewing-db-changes' into 'master'

Added Rubocop config for background migrations

See merge request gitlab-org/gitlab-ce!15576

lib/gitlab/background_migration/.rubocop.yml

+# For background migrations we define a custom set of rules to make it less
+# difficult to review these migrations. To reduce the complexity of these
+# migrations some rules may be stricter than the defaults set in the root
+# .rubocop.yml file.
+---
+inherit_from: ../../../.rubocop.yml
+
+Metrics/AbcSize:
+  Enabled: true
+  Max: 30
+  Details: >
+    Code that involves a lot of branches can be very hard to wrap your head
+    around.
+
+Metrics/PerceivedComplexity:
+  Enabled: true
+
+Metrics/LineLength:
+  Enabled: true
+  Details: >
+    Long lines are very hard to read and make it more difficult to review
+    changes.
+
+Metrics/MethodLength:
+  Enabled: true
+  Max: 30
+  Details: >
+    Long methods can be very hard to review. Consider splitting this method up
+    into separate methods.
+
+Metrics/ClassLength:
+  Enabled: true
+  Details: >
+    Long classes can be very hard to review. Consider splitting this class up
+    into multiple classes.
+
+Metrics/BlockLength:
+  Enabled: true
+  Details: >
+    Long blocks can be hard to read. Consider splitting the code into separate
+    methods.
+
+Style/Documentation:
+  Enabled: true
+  Details: >
+    Adding documentation makes it easier to figure out what a migration is
+    supposed to do.
+
+Style/FrozenStringLiteralComment:
+  Enabled: true
+  Details: >-
+    This removes the need for calling "freeze", reducing noise in the code.

lib/gitlab/background_migration/create_fork_network_memberships_range.rb

+# frozen_string_literal: true
+# rubocop:disable Metrics/LineLength
+# rubocop:disable Style/Documentation
+
 module Gitlab
   module BackgroundMigration
     class CreateForkNetworkMembershipsRange

lib/gitlab/background_migration/create_gpg_key_subkeys_from_gpg_keys.rb

+# frozen_string_literal: true
+# rubocop:disable Metrics/LineLength
+# rubocop:disable Style/Documentation
+
 class Gitlab::BackgroundMigration::CreateGpgKeySubkeysFromGpgKeys
   class GpgKey < ActiveRecord::Base
     self.table_name = 'gpg_keys'

lib/gitlab/background_migration/delete_conflicting_redirect_routes_range.rb

+# frozen_string_literal: true
+# rubocop:disable Metrics/LineLength
+# rubocop:disable Style/Documentation
+
 module Gitlab
   module BackgroundMigration
     class DeleteConflictingRedirectRoutesRange

lib/gitlab/background_migration/deserialize_merge_request_diffs_and_commits.rb

+# frozen_string_literal: true
+# rubocop:disable Metrics/MethodLength
+# rubocop:disable Metrics/LineLength
+# rubocop:disable Metrics/AbcSize
+# rubocop:disable Style/Documentation
+
 module Gitlab
   module BackgroundMigration
     class DeserializeMergeRequestDiffsAndCommits

lib/gitlab/background_migration/migrate_build_stage_id_reference.rb

+# frozen_string_literal: true
+# rubocop:disable Style/Documentation
+
 module Gitlab
   module BackgroundMigration
     class MigrateBuildStageIdReference

lib/gitlab/background_migration/migrate_events_to_push_event_payloads.rb

+# frozen_string_literal: true
+# rubocop:disable Metrics/LineLength
+# rubocop:disable Style/Documentation
+
 module Gitlab
   module BackgroundMigration
     # Class that migrates events for the new push event payloads setup. All

lib/gitlab/background_migration/migrate_stage_status.rb

+# frozen_string_literal: true
+# rubocop:disable Metrics/AbcSize
+# rubocop:disable Style/Documentation
+
 module Gitlab
   module BackgroundMigration
     class MigrateStageStatus

lib/gitlab/background_migration/migrate_system_uploads_to_new_folder.rb

+# frozen_string_literal: true
+# rubocop:disable Metrics/LineLength
+# rubocop:disable Style/Documentation
+
 module Gitlab
   module BackgroundMigration
     class MigrateSystemUploadsToNewFolder

lib/gitlab/background_migration/move_personal_snippet_files.rb

+# frozen_string_literal: true
+# rubocop:disable Metrics/LineLength
+# rubocop:disable Style/Documentation
+
 module Gitlab
   module BackgroundMigration
     class MovePersonalSnippetFiles

lib/gitlab/background_migration/normalize_ldap_extern_uids_range.rb

+# frozen_string_literal: true
+# rubocop:disable Metrics/MethodLength
+# rubocop:disable Metrics/LineLength
+# rubocop:disable Metrics/ClassLength
+# rubocop:disable Metrics/BlockLength
+# rubocop:disable Style/Documentation
+
 module Gitlab
   module BackgroundMigration
     class NormalizeLdapExternUidsRange

lib/gitlab/background_migration/populate_fork_networks_range.rb

+# frozen_string_literal: true
+# rubocop:disable Metrics/MethodLength
+# rubocop:disable Metrics/LineLength
+# rubocop:disable Style/Documentation
+
 module Gitlab
   module BackgroundMigration
     class PopulateForkNetworksRange

lib/gitlab/background_migration/populate_merge_requests_latest_merge_request_diff_id.rb

+# frozen_string_literal: true
+# rubocop:disable Style/Documentation
+
 module Gitlab
   module BackgroundMigration
     class PopulateMergeRequestsLatestMergeRequestDiffId