Add a column to track when a project default branch changes

db/migrate/20210705124128_add_project_settings_previous_default_branch.rb

+# frozen_string_literal: true
+
+class AddProjectSettingsPreviousDefaultBranch < ActiveRecord::Migration[6.1]
+  include Gitlab::Database::MigrationHelpers
+
+  # rubocop:disable Migration/AddLimitToTextColumns
+  # limit is added in 20210707173645_add_project_settings_previous_default_branch_text_limit
+  def up
+    with_lock_retries do
+      add_column :project_settings, :previous_default_branch, :text
+    end
+  end
+  # rubocop:enable Migration/AddLimitToTextColumns
+
+  def down
+    with_lock_retries do
+      remove_column :project_settings, :previous_default_branch
+    end
+  end
+end

db/migrate/20210707173645_add_project_settings_previous_default_branch_text_limit.rb

+# frozen_string_literal: true
+
+class AddProjectSettingsPreviousDefaultBranchTextLimit < ActiveRecord::Migration[6.1]
+  include Gitlab::Database::MigrationHelpers
+
+  disable_ddl_transaction!
+
+  def up
+    add_text_limit :project_settings, :previous_default_branch, 4096
+  end
+
+  def down
+    remove_text_limit :project_settings, :previous_default_branch
+  end
+end

db/schema_migrations/20210705124128

+02aea8fe759614bc3aa751e023aa508963f8183366f6d6f518bbccc2d85ec1a1
\ No newline at end of file

db/schema_migrations/20210707173645

+e440dac0e14df7309c84e72b98ed6373c712901dc66310a474979e0fce7dc59c
\ No newline at end of file

db/structure.sql

@@ -17081,6 +17081,8 @@ CREATE TABLE project_settings (
     prevent_merge_without_jira_issue boolean DEFAULT false NOT NULL,
     cve_id_request_enabled boolean DEFAULT true NOT NULL,
     mr_default_target_self boolean DEFAULT false NOT NULL,
+    previous_default_branch text,
+    CONSTRAINT check_3a03e7557a CHECK ((char_length(previous_default_branch) <= 4096)),
     CONSTRAINT check_bde223416c CHECK ((show_default_award_emojis IS NOT NULL))
 );
 

spec/requests/api/project_attributes.yml

@@ -137,6 +137,7 @@ project_setting:
     - has_confluence
     - has_vulnerabilities
     - prevent_merge_without_jira_issue
+    - previous_default_branch
     - project_id
     - push_rule_id
     - show_default_award_emojis