1 files changed, 69 insertions, 0 deletions
diff --git a/railties/lib/rails/generators/migration.rb b/railties/lib/rails/generators/migration.rb
new file mode 100644
index 0000000000..87f2e1d42b
--- /dev/null
+++ b/railties/lib/rails/generators/migration.rb
@@ -0,0 +1,69 @@
+require 'active_support/concern'
+require 'rails/generators/actions/create_migration'
+
+module Rails
+  module Generators
+    # Holds common methods for migrations. It assumes that migrations have the
+    # [0-9]*_name format and can be used by other frameworks (like Sequel)
+    # just by implementing the next migration version method.
+    module Migration
+      extend ActiveSupport::Concern
+      attr_reader :migration_number, :migration_file_name, :migration_class_name
+
+      module ClassMethods #:nodoc:
+        def migration_lookup_at(dirname)
+          Dir.glob("#{dirname}/[0-9]*_*.rb")
+        end
+
+        def migration_exists?(dirname, file_name)
+          migration_lookup_at(dirname).grep(/\d+_#{file_name}.rb$/).first
+        end
+
+        def current_migration_number(dirname)
+          migration_lookup_at(dirname).collect do |file|
+            File.basename(file).split("_").first.to_i
+          end.max.to_i
+        end
+
+        def next_migration_number(dirname)
+          raise NotImplementedError
+        end
+      end
+
+      def create_migration(destination, data, config = {}, &block)
+        action Rails::Generators::Actions::CreateMigration.new(self, destination, block || data.to_s, config)
+      end
+
+      def set_migration_assigns!(destination)
+        destination = File.expand_path(destination, self.destination_root)
+
+        migration_dir = File.dirname(destination)
+        @migration_number     = self.class.next_migration_number(migration_dir)
+        @migration_file_name  = File.basename(destination, '.rb')
+        @migration_class_name = @migration_file_name.camelize
+      end
+
+      # Creates a migration template at the given destination. The difference
+      # to the default template method is that the migration version is appended
+      # to the destination file name.
+      #
+      # The migration version, migration file name, migration class name are
+      # available as instance variables in the template to be rendered.
+      #
+      #   migration_template "migration.rb", "db/migrate/add_foo_to_bar.rb"
+      def migration_template(source, destination, config = {})
+        source  = File.expand_path(find_in_source_paths(source.to_s))
+
+        set_migration_assigns!(destination)
+        context = instance_eval('binding')
+
+        dir, base = File.split(destination)
+        numbered_destination = File.join(dir, ["%migration_number%", base].join('_'))
+
+        create_migration numbered_destination, nil, config do
+          ERB.new(::File.binread(source), nil, '-', '@output_buffer').result(context)
+        end
+      end
+    end
+  end
+end