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

1 files changed, 16 insertions, 4 deletions

diff --git a/activerecord/lib/rails/generators/active_record/migration/templates/migration.rb b/activerecord/lib/rails/generators/active_record/migration/templates/migration.rb
index b1a0f83b5f..34eaffcb0f 100644
--- a/activerecord/lib/rails/generators/active_record/migration/templates/migration.rb
+++ b/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