FIX: Couldn't migrate database from nothing due to I18n

Since I18n has a DB backend now, I've introduced a helper we can use to
skip overrides in certain situations. Otherwise migration from empty
databases was broken.

db/migrate/20140120155706_add_lounge_category.rb

@@ -1,11 +1,13 @@
 class AddLoungeCategory < ActiveRecord::Migration
   def up
-    unless Rails.env.test?
+    return if Rails.env.test?
+
+    I18n.backend.overrides_disabled do
       result = Category.exec_sql "SELECT 1 FROM site_settings where name = 'lounge_category_id'"
       if result.count == 0
-        description = I18n.t('vip_category_description')
+        description = I18n.t('vip_category_description', skip_overrides: true)
 
-        default_name = I18n.t('vip_category_name')
+        default_name = I18n.t('vip_category_name', skip_overrides: true)
         name = if Category.exec_sql("SELECT 1 FROM categories where name = '#{default_name}'").count == 0
           default_name
         else

db/migrate/20140122043508_add_meta_category.rb

@@ -1,6 +1,8 @@
 class AddMetaCategory < ActiveRecord::Migration
   def up
-    unless Rails.env.test?
+    return if Rails.env.test?
+
+    I18n.backend.overrides_disabled do
       result = Category.exec_sql "SELECT 1 FROM site_settings where name = 'meta_category_id'"
       if result.count == 0
         description = I18n.t('meta_category_description')

db/migrate/20140227201005_add_staff_category.rb

@@ -1,6 +1,8 @@
 class AddStaffCategory < ActiveRecord::Migration
   def up
-    unless Rails.env.test?
+    return if Rails.env.test?
+
+    I18n.backend.overrides_disabled do
       result = Category.exec_sql "SELECT 1 FROM site_settings where name = 'staff_category_id'"
       if result.count == 0
         description = I18n.t('staff_category_description')

db/migrate/20141014191645_fix_tos_name.rb

@@ -1,6 +1,8 @@
 class FixTosName < ActiveRecord::Migration
   def up
-    execute ActiveRecord::Base.sql_fragment('UPDATE user_fields SET name = ? WHERE name = ?', I18n.t('terms_of_service.title'), I18n.t("terms_of_service.signup_form_message"))
+    I18n.backend.overrides_disabled do
+      execute ActiveRecord::Base.sql_fragment('UPDATE user_fields SET name = ? WHERE name = ?', I18n.t('terms_of_service.title'), I18n.t("terms_of_service.signup_form_message"))
+    end
 
   end
 end

db/migrate/20150728210202_migrate_old_moderator_posts.rb

@@ -1,9 +1,11 @@
 class MigrateOldModeratorPosts < ActiveRecord::Migration
 
   def migrate_key(action_code)
-    text = I18n.t("topic_statuses.#{action_code.gsub('.', '_')}")
+    I18n.backend.overrides_disabled do
+      text = I18n.t("topic_statuses.#{action_code.gsub('.', '_')}")
 
-    execute "UPDATE posts SET action_code = '#{action_code}', raw = '', cooked = '', post_type = 3 where post_type = 2 AND raw = #{ActiveRecord::Base.connection.quote(text)}"
+      execute "UPDATE posts SET action_code = '#{action_code}', raw = '', cooked = '', post_type = 3 where post_type = 2 AND raw = #{ActiveRecord::Base.connection.quote(text)}"
+    end
   end
 
   def up

db/migrate/20150729150523_migrate_auto_close_posts.rb

@@ -1,16 +1,18 @@
 class MigrateAutoClosePosts < ActiveRecord::Migration
   def up
-    strings = []
-    %w(days hours lastpost_days lastpost_hours lastpost_minutes).map do |k|
-      strings << I18n.t("topic_statuses.autoclosed_enabled_#{k}.one")
-      strings << I18n.t("topic_statuses.autoclosed_enabled_#{k}.other").sub("%{count}", "\\d+")
+    I18n.backend.overrides_disabled do
+      strings = []
+      %w(days hours lastpost_days lastpost_hours lastpost_minutes).map do |k|
+        strings << I18n.t("topic_statuses.autoclosed_enabled_#{k}.one")
+        strings << I18n.t("topic_statuses.autoclosed_enabled_#{k}.other").sub("%{count}", "\\d+")
+      end
+
+      sql = "UPDATE posts SET action_code = 'autoclosed.enabled', post_type = 3 "
+      sql << "WHERE post_type = 2 AND ("
+      sql << strings.map {|s| "raw ~* #{ActiveRecord::Base.connection.quote(s)}" }.join(' OR ')
+      sql << ")"
+
+      execute sql
     end
-
-    sql = "UPDATE posts SET action_code = 'autoclosed.enabled', post_type = 3 "
-    sql << "WHERE post_type = 2 AND ("
-    sql << strings.map {|s| "raw ~* #{ActiveRecord::Base.connection.quote(s)}" }.join(' OR ')
-    sql << ")"
-
-    execute sql
   end
 end

lib/i18n/backend/discourse_i18n.rb

@@ -5,6 +5,10 @@ module I18n
     class DiscourseI18n < I18n::Backend::Simple
       include I18n::Backend::Pluralization
 
+      def initialize
+        @overrides_enabled = true
+      end
+
       def available_locales
         # in case you are wondering this is:
         # Dir.glob( File.join(Rails.root, 'config', 'locales', 'client.*.yml') )
@@ -30,6 +34,15 @@ module I18n
         @overrides[locale]
       end
 
+      # In some environments such as migrations we don't want to use overrides.
+      # Use this to disable them over a block of ruby code
+      def overrides_disabled
+        @overrides_enabled = false
+        yield
+      ensure
+        @overrides_enabled = true
+      end
+
       # force explicit loading
       def load_translations(*filenames)
         unless filenames.empty?
@@ -42,7 +55,7 @@ module I18n
       end
 
       def translate(locale, key, options = {})
-        overrides_for(locale)[key] || super(locale, key, options)
+        (@overrides_enabled && overrides_for(locale)[key]) || super(locale, key, options)
       end
 
       def exists?(locale, key)