make db:migrate:redo rake task accept an optional VERSION to target t…

…hat specific migration to redo

Signed-off-by: Michael Koziarski <michael@koziarski.com>

railties/lib/tasks/databases.rake

@@ -113,8 +113,16 @@ namespace :db do
   end
 
   namespace :migrate do
-    desc  'Rollbacks the database one migration and re migrate up. If you want to rollback more than one step, define STEP=x'
-    task :redo => [ 'db:rollback', 'db:migrate' ]
+    desc  'Rollbacks the database one migration and re migrate up. If you want to rollback more than one step, define STEP=x. Target specific version with VERSION=x.'
+    task :redo => :environment do
+      if ENV["VERSION"]
+        Rake::Task["db:migrate:down"].invoke
+        Rake::Task["db:migrate:up"].invoke
+      else
+        Rake::Task["db:rollback"].invoke
+        Rake::Task["db:migrate"].invoke
+      end
+    end
 
     desc 'Resets your database using your migrations for the current environment'
     task :reset => ["db:drop", "db:create", "db:migrate"]