add convenience methods for checking migrations

if a rails project needs to be migrated ActiveRecord::Migrator.needs_migration? will be true or false if the current version matches the last version.

activerecord/lib/active_record/migration.rb

@@ -605,6 +605,14 @@ module ActiveRecord
         end
       end
 
+      def needs_migration?
+        current_version != last_version
+      end
+
+      def last_version
+        migrations(migrations_paths).last.try(:version)||0
+      end
+
       def proper_table_name(name)
         # Use the Active Record objects own table_name, or pre/suffix from ActiveRecord::Base if name is a symbol/string
         name.table_name rescue "#{ActiveRecord::Base.table_name_prefix}#{name}#{ActiveRecord::Base.table_name_suffix}"

activerecord/test/cases/migration_test.rb

@@ -56,6 +56,21 @@ class MigrationTest < ActiveRecord::TestCase
     Person.reset_column_information
   end
 
+  def test_migrator_versions
+    migrations_path = MIGRATIONS_ROOT + "/valid"
+    ActiveRecord::Migrator.migrations_paths = migrations_path
+
+    ActiveRecord::Migrator.up(migrations_path)
+    assert_equal 3, ActiveRecord::Migrator.current_version
+    assert_equal 3, ActiveRecord::Migrator.last_version
+    assert_equal false, ActiveRecord::Migrator.needs_migration?
+
+    ActiveRecord::Migrator.down(MIGRATIONS_ROOT + "/valid")
+    assert_equal 0, ActiveRecord::Migrator.current_version
+    assert_equal 3, ActiveRecord::Migrator.last_version
+    assert_equal true, ActiveRecord::Migrator.needs_migration?
+  end
+
   def test_create_table_with_force_true_does_not_drop_nonexisting_table
     if Person.connection.table_exists?(:testings2)
       Person.connection.drop_table :testings2