Added Rubocop config for background migrationsreviewing-db-changes

This adds a Rubocop configuration file specific to
lib/gitlab/background_migrations. This configuration will be used to
(hopefully) make reviewing background migrations easier by enforcing
stricter rules compared to the rest of GitLab. Because this
configuration is directory specific it will only affect background
migrations.

13 files changed, 104 insertions, 0 deletions

diff --git a/lib/gitlab/background_migration/.rubocop.yml b/lib/gitlab/background_migration/.rubocop.yml
new file mode 100644
index 00000000000..8242821cedc
--- /dev/null
+++ b/lib/gitlab/background_migration/.rubocop.yml
@@ -0,0 +1,52 @@
+# 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.
diff --git a/lib/gitlab/background_migration/create_fork_network_memberships_range.rb b/lib/gitlab/background_migration/create_fork_network_memberships_range.rb
index 67a39d28944..03b17b319fa 100644
--- a/lib/gitlab/background_migration/create_fork_network_memberships_range.rb
+++ b/lib/gitlab/background_migration/create_fork_network_memberships_range.rb
@@ -1,3 +1,7 @@
+# frozen_string_literal: true
+# rubocop:disable Metrics/LineLength
+# rubocop:disable Style/Documentation
+
 module Gitlab
   module BackgroundMigration
     class CreateForkNetworkMembershipsRange
diff --git a/lib/gitlab/background_migration/create_gpg_key_subkeys_from_gpg_keys.rb b/lib/gitlab/background_migration/create_gpg_key_subkeys_from_gpg_keys.rb
index e94719db72e..c2bf42f846d 100644
--- a/lib/gitlab/background_migration/create_gpg_key_subkeys_from_gpg_keys.rb
+++ b/lib/gitlab/background_migration/create_gpg_key_subkeys_from_gpg_keys.rb
@@ -1,3 +1,7 @@
+# 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'
diff --git a/lib/gitlab/background_migration/delete_conflicting_redirect_routes_range.rb b/lib/gitlab/background_migration/delete_conflicting_redirect_routes_range.rb
index b1411be3016..a1af045a71f 100644
--- a/lib/gitlab/background_migration/delete_conflicting_redirect_routes_range.rb
+++ b/lib/gitlab/background_migration/delete_conflicting_redirect_routes_range.rb
@@ -1,3 +1,7 @@
+# frozen_string_literal: true
+# rubocop:disable Metrics/LineLength
+# rubocop:disable Style/Documentation
+
 module Gitlab
   module BackgroundMigration
     class DeleteConflictingRedirectRoutesRange
diff --git a/lib/gitlab/background_migration/deserialize_merge_request_diffs_and_commits.rb b/lib/gitlab/background_migration/deserialize_merge_request_diffs_and_commits.rb
index 380802258f5..fd5cbf76e47 100644
--- a/lib/gitlab/background_migration/deserialize_merge_request_diffs_and_commits.rb
+++ b/lib/gitlab/background_migration/deserialize_merge_request_diffs_and_commits.rb
@@ -1,3 +1,9 @@
+# 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
diff --git a/lib/gitlab/background_migration/migrate_build_stage_id_reference.rb b/lib/gitlab/background_migration/migrate_build_stage_id_reference.rb
index 91540127ea9..0a8a4313cd5 100644
--- a/lib/gitlab/background_migration/migrate_build_stage_id_reference.rb
+++ b/lib/gitlab/background_migration/migrate_build_stage_id_reference.rb
@@ -1,3 +1,6 @@
+# frozen_string_literal: true
+# rubocop:disable Style/Documentation
+
 module Gitlab
   module BackgroundMigration
     class MigrateBuildStageIdReference
diff --git a/lib/gitlab/background_migration/migrate_events_to_push_event_payloads.rb b/lib/gitlab/background_migration/migrate_events_to_push_event_payloads.rb
index 432f7c3e706..84ac00f1a5c 100644
--- a/lib/gitlab/background_migration/migrate_events_to_push_event_payloads.rb
+++ b/lib/gitlab/background_migration/migrate_events_to_push_event_payloads.rb
@@ -1,3 +1,7 @@
+# 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
diff --git a/lib/gitlab/background_migration/migrate_stage_status.rb b/lib/gitlab/background_migration/migrate_stage_status.rb
index b1ff0900709..0e5c7f092f2 100644
--- a/lib/gitlab/background_migration/migrate_stage_status.rb
+++ b/lib/gitlab/background_migration/migrate_stage_status.rb
@@ -1,3 +1,7 @@
+# frozen_string_literal: true
+# rubocop:disable Metrics/AbcSize
+# rubocop:disable Style/Documentation
+
 module Gitlab
   module BackgroundMigration
     class MigrateStageStatus
diff --git a/lib/gitlab/background_migration/migrate_system_uploads_to_new_folder.rb b/lib/gitlab/background_migration/migrate_system_uploads_to_new_folder.rb
index 0881244ed49..7f243073fd0 100644
--- a/lib/gitlab/background_migration/migrate_system_uploads_to_new_folder.rb
+++ b/lib/gitlab/background_migration/migrate_system_uploads_to_new_folder.rb
@@ -1,3 +1,7 @@
+# frozen_string_literal: true
+# rubocop:disable Metrics/LineLength
+# rubocop:disable Style/Documentation
+
 module Gitlab
   module BackgroundMigration
     class MigrateSystemUploadsToNewFolder
diff --git a/lib/gitlab/background_migration/move_personal_snippet_files.rb b/lib/gitlab/background_migration/move_personal_snippet_files.rb
index 07cec96bcc3..a4ef51fd0e8 100644
--- a/lib/gitlab/background_migration/move_personal_snippet_files.rb
+++ b/lib/gitlab/background_migration/move_personal_snippet_files.rb
@@ -1,3 +1,7 @@
+# frozen_string_literal: true
+# rubocop:disable Metrics/LineLength
+# rubocop:disable Style/Documentation
+
 module Gitlab
   module BackgroundMigration
     class MovePersonalSnippetFiles
diff --git a/lib/gitlab/background_migration/normalize_ldap_extern_uids_range.rb b/lib/gitlab/background_migration/normalize_ldap_extern_uids_range.rb
index bc53e6d7f94..85749366bfd 100644
--- a/lib/gitlab/background_migration/normalize_ldap_extern_uids_range.rb
+++ b/lib/gitlab/background_migration/normalize_ldap_extern_uids_range.rb
@@ -1,3 +1,10 @@
+# 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
diff --git a/lib/gitlab/background_migration/populate_fork_networks_range.rb b/lib/gitlab/background_migration/populate_fork_networks_range.rb
index 2ef3a207dd3..f8508b5fbdf 100644
--- a/lib/gitlab/background_migration/populate_fork_networks_range.rb
+++ b/lib/gitlab/background_migration/populate_fork_networks_range.rb
@@ -1,3 +1,8 @@
+# frozen_string_literal: true
+# rubocop:disable Metrics/MethodLength
+# rubocop:disable Metrics/LineLength
+# rubocop:disable Style/Documentation
+
 module Gitlab
   module BackgroundMigration
     class PopulateForkNetworksRange
diff --git a/lib/gitlab/background_migration/populate_merge_requests_latest_merge_request_diff_id.rb b/lib/gitlab/background_migration/populate_merge_requests_latest_merge_request_diff_id.rb
index 7e109e96e73..dcac355e1b0 100644
--- a/lib/gitlab/background_migration/populate_merge_requests_latest_merge_request_diff_id.rb
+++ b/lib/gitlab/background_migration/populate_merge_requests_latest_merge_request_diff_id.rb
@@ -1,3 +1,6 @@
+# frozen_string_literal: true
+# rubocop:disable Style/Documentation
+
 module Gitlab
   module BackgroundMigration
     class PopulateMergeRequestsLatestMergeRequestDiffId