Add default_branch_name column to namespace_settings table

changelogs/unreleased/251935-add-default_branch_name-column-to-namespace_settings-table.yml

+---
+title: Add :default_branch_name column to namespace_settings
+merge_request: 42778
+author:
+type: added

db/migrate/20200919200318_add_default_branch_name_to_namespace_settings.rb

+# frozen_string_literal: true
+
+class AddDefaultBranchNameToNamespaceSettings < ActiveRecord::Migration[6.0]
+  DOWNTIME = false
+
+  # rubocop:disable Migration/AddLimitToTextColumns
+
+  # limit is added in 20200919204155_add_text_limit_to_namespace_settings_default_branch_name
+  #
+  def change
+    add_column :namespace_settings, :default_branch_name, :text
+  end
+
+  # rubocop:enable Migration/AddLimitToTextColumns
+end

db/migrate/20200919204155_add_text_limit_to_namespace_settings_default_branch_name.rb

+# frozen_string_literal: true
+
+class AddTextLimitToNamespaceSettingsDefaultBranchName < ActiveRecord::Migration[6.0]
+  include Gitlab::Database::MigrationHelpers
+
+  DOWNTIME = false
+
+  disable_ddl_transaction!
+
+  def up
+    add_text_limit :namespace_settings, :default_branch_name, 255
+  end
+
+  def down
+    # Down is required as `add_text_limit` is not reversible
+    #
+    remove_text_limit :namespace_settings, :default_branch_name
+  end
+end

db/schema_migrations/20200919200318

+f33c66297ca7848c576778dc275e42801f5f9d7cdcf8c4d2fb205d4eb9770937
\ No newline at end of file

db/schema_migrations/20200919204155

+097cb7a36fdc831045f3a33a047f8bda6474b8165ef5fc95dbdeea45d0ac04a3
\ No newline at end of file

db/structure.sql

@@ -13562,7 +13562,9 @@ CREATE TABLE namespace_settings (
     updated_at timestamp with time zone NOT NULL,
     namespace_id integer NOT NULL,
     prevent_forking_outside_group boolean DEFAULT false NOT NULL,
-    allow_mfa_for_subgroups boolean DEFAULT true NOT NULL
+    allow_mfa_for_subgroups boolean DEFAULT true NOT NULL,
+    default_branch_name text,
+    CONSTRAINT check_0ba93c78c7 CHECK ((char_length(default_branch_name) <= 255))
 );
 
 CREATE TABLE namespace_statistics (