Switch to simpler migration structure via Engine, Thanks @parndt

UPGRADING

@@ -2,7 +2,6 @@ When upgrading
 
 Re-run the migrations generator
 
-    rails generate acts_as_taggable_on:migration
-    rake db:migrate
+    rake railties:install:migrations FROM=acts_as_taggable_on_engine db:migrate
 
 It will create any new migrations and skip existing ones

lib/generators/acts_as_taggable_on/migration/templates/active_record/migration02-add_missing_unique_indices.rb → db/migrate/2_add_missing_unique_indices.rb

@@ -1,14 +1,16 @@
-class ActsAsTaggableOnAddMissingUniqueIndices < ActiveRecord::Migration
+class AddMissingUniqueIndices < ActiveRecord::Migration
 
   def self.up
+    add_index :tags, :name, unique: true
+
     remove_index :taggings, :tag_id
     remove_index :taggings, [:taggable_id, :taggable_type, :context]
-    add_index :tags, :name, unique: true
     add_index :taggings, [:tag_id, :taggable_id, :taggable_type, :context, :tagger_id, :tagger_type], unique: true, name: 'tagging_idx'
    end
 
   def self.down
     remove_index :tags, :name
+
     remove_index :taggings, name: 'tagging_idx'
     add_index :taggings, :tag_id
     add_index :taggings, [:taggable_id, :taggable_type, :context]

lib/acts-as-taggable-on.rb

@@ -48,6 +48,7 @@ def self.setup
 require "acts_as_taggable_on/tag_list"
 require "acts_as_taggable_on/tags_helper"
 require "acts_as_taggable_on/tagging"
+require 'acts_as_taggable_on/engine'
 
 ActiveSupport.on_load(:active_record) do
   extend ActsAsTaggableOn::Compatibility
@@ -57,4 +58,3 @@ def self.setup
 ActiveSupport.on_load(:action_view) do
   include ActsAsTaggableOn::TagsHelper
 end
-

lib/acts_as_taggable_on/engine.rb

@@ -0,0 +1,6 @@
+require 'rails/engine'
+module ActsAsTaggableOn
+  class Engine < Rails::Engine
+
+  end
+end