Support creating a table migration generator

Sometimes you want to create a table without an associated model and
test, which is also not a join table. With this commit, you can now
do that.

Example:

    rails g migration create_posts title:string
or
    rails g migration CreatePosts title:string

This commit also moves the template the model generator uses for the
migration to the migration templates folder, as it seems a more
sensible place for it now that it is shared code.

3 files changed, 10 insertions, 3 deletions

diff --git a/activerecord/lib/rails/generators/active_record/migration/migration_generator.rb b/activerecord/lib/rails/generators/active_record/migration/migration_generator.rb
index 5f1dbe36d6..b967bb6e0f 100644
--- a/activerecord/lib/rails/generators/active_record/migration/migration_generator.rb
+++ b/activerecord/lib/rails/generators/active_record/migration/migration_generator.rb
@@ -8,13 +8,14 @@ module ActiveRecord
       def create_migration_file
         set_local_assigns!
         validate_file_name!
-        migration_template "migration.rb", "db/migrate/#{file_name}.rb"
+        migration_template @migration_template, "db/migrate/#{file_name}.rb"
       end
 
       protected
       attr_reader :migration_action, :join_tables
 
       def set_local_assigns!
+        @migration_template = "migration.rb"
         case file_name
         when /^(add|remove)_.*_(?:to|from)_(.*)/
           @migration_action = $1
@@ -26,6 +27,9 @@ module ActiveRecord
 
             set_index_names
           end
+        when /^create_(.+)/
+          @table_name = $1.pluralize
+          @migration_template = "create_table_migration.rb"
         end
       end
 
@@ -44,7 +48,10 @@ module ActiveRecord
       end
 
       private
-
+        def attributes_with_index
+          attributes.select { |a| !a.reference? && a.has_index? }
+        end
+        
         def validate_file_name!
           unless file_name =~ /^[_a-z0-9]+$/
             raise IllegalMigrationNameError.new(file_name)
diff --git a/activerecord/lib/rails/generators/active_record/model/templates/migration.rb b/activerecord/lib/rails/generators/active_record/migration/templates/create_table_migration.rb
index 3a3cf86d73..3a3cf86d73 100644
--- a/activerecord/lib/rails/generators/active_record/model/templates/migration.rb
+++ b/activerecord/lib/rails/generators/active_record/migration/templates/create_table_migration.rb
diff --git a/activerecord/lib/rails/generators/active_record/model/model_generator.rb b/activerecord/lib/rails/generators/active_record/model/model_generator.rb
index 5f36181694..40e134e626 100644
--- a/activerecord/lib/rails/generators/active_record/model/model_generator.rb
+++ b/activerecord/lib/rails/generators/active_record/model/model_generator.rb
@@ -15,7 +15,7 @@ module ActiveRecord
       def create_migration_file
         return unless options[:migration] && options[:parent].nil?
         attributes.each { |a| a.attr_options.delete(:index) if a.reference? && !a.has_index? } if options[:indexes] == false
-        migration_template "migration.rb", "db/migrate/create_#{table_name}.rb"
+        migration_template "../../migration/templates/create_table_migration.rb", "db/migrate/create_#{table_name}.rb"
       end
 
       def create_model_file