Add references statements to migration generator

AddXXXToYYY/RemoveXXXFromYYY migrations are produced with references
statements, for instance

    rails g migration AddReferencesToProducts user:references
supplier:references{polymorphic}

will generate the migration with:

    add_reference :products, :user, index: true
    add_reference :products, :supplier, polymorphic: true, index: true

activerecord/lib/rails/generators/active_record/migration/templates/migration.rb

@@ -2,30 +2,42 @@ class <%= migration_class_name %> < ActiveRecord::Migration
 <%- if migration_action == 'add' -%>
   def change
 <% attributes.each do |attribute| -%>
+  <%- if attribute.reference? -%>
+    add_reference :<%= table_name %>, :<%= attribute.name %><%= attribute.inject_options %>
+  <%- else -%>
     add_column :<%= table_name %>, :<%= attribute.name %>, :<%= attribute.type %><%= attribute.inject_options %>
     <%- if attribute.has_index? -%>
     add_index :<%= table_name %>, :<%= attribute.index_name %><%= attribute.inject_index_options %>
     <%- end -%>
+  <%- end -%>
 <%- end -%>
   end
 <%- else -%>
   def up
 <% attributes.each do |attribute| -%>
-  <%- if migration_action -%>
-    <%= migration_action %>_column :<%= table_name %>, :<%= attribute.name %>
+<%- if migration_action -%>
+  <%- if attribute.reference? -%>
+    remove_reference :<%= table_name %>, :<%= attribute.name %><%= ', polymorphic: true' if attribute.polymorphic? %>
+  <%- else -%>
+    remove_column :<%= table_name %>, :<%= attribute.name %>
   <%- end -%>
+<%- end -%>
 <%- end -%>
   end
 
   def down
 <% attributes.reverse.each do |attribute| -%>
-  <%- if migration_action -%>
+<%- if migration_action -%>
+  <%- if attribute.reference? -%>
+    add_reference :<%= table_name %>, :<%= attribute.name %><%= attribute.inject_options %>
+  <%- else -%>
     add_column :<%= table_name %>, :<%= attribute.name %>, :<%= attribute.type %><%= attribute.inject_options %>
     <%- if attribute.has_index? -%>
     add_index :<%= table_name %>, :<%= attribute.index_name %><%= attribute.inject_index_options %>
     <%- end -%>
   <%- end -%>
+<%- end -%>
 <%- end -%>
   end
 <%- end -%>
-end
+end
\ No newline at end of file

railties/CHANGELOG.md

 ## Rails 4.0.0 (unreleased) ##
 
+*   The migration generator will now produce AddXXXToYYY/RemoveXXXFromYYY migrations with references statements, for instance
+
+        rails g migration AddReferencesToProducts user:references supplier:references{polymorphic}
+
+    will generate the migration with:
+
+        add_reference :products, :user, index: true
+        add_reference :products, :supplier, polymorphic: true, index: true
+
+    *Aleksey Magusev*
+
 *   Allow scaffold/model/migration generators to accept a `polymorphic` modifier
     for `references`/`belongs_to`, for instance
 

railties/test/generators/migration_generator_test.rb

@@ -76,6 +76,23 @@ def test_remove_migration_with_attributes
     end
   end
 
+  def test_remove_migration_with_references_options
+    migration = "remove_references_from_books"
+    run_generator [migration, "author:belongs_to", "distributor:references{polymorphic}"]
+
+    assert_migration "db/migrate/#{migration}.rb" do |content|
+      assert_method :up, content do |up|
+        assert_match(/remove_reference :books, :author/, up)
+        assert_match(/remove_reference :books, :distributor, polymorphic: true/, up)
+      end
+
+      assert_method :down, content do |down|
+        assert_match(/add_reference :books, :author, index: true/, down)
+        assert_match(/add_reference :books, :distributor, polymorphic: true, index: true/, down)
+      end
+    end
+  end
+
   def test_add_migration_with_attributes_and_indices
     migration = "add_title_with_index_and_body_to_posts"
     run_generator [migration, "title:string:index", "body:text", "user_id:integer:uniq"]
@@ -138,6 +155,18 @@ def test_add_migration_with_attributes_index_declaration_and_attribute_options
     end
   end
 
+  def test_add_migration_with_references_options
+    migration = "add_references_to_books"
+    run_generator [migration, "author:belongs_to", "distributor:references{polymorphic}"]
+
+    assert_migration "db/migrate/#{migration}.rb" do |content|
+      assert_method :change, content do |up|
+        assert_match(/add_reference :books, :author, index: true/, up)
+        assert_match(/add_reference :books, :distributor, polymorphic: true, index: true/, up)
+      end
+    end
+  end
+
   def test_should_create_empty_migrations_if_name_not_start_with_add_or_remove
     migration = "create_books"
     run_generator [migration, "title:string", "content:text"]