ruby script/plugin install http://stochasticbytes.com/svn/r_migrations/

This plugin adds a "history" table that keeps track of which migrations have been run and which have not. Migrations with lower (or equal) versions than the current db version will be retroactively run. Conversely, if migrating to a previous db version, migrations that have not previously been run (i.e. do not have an entry in the history table) will not be run.

This plugin defines a handful of Rake tasks to examine and manage the history table.

List what migrations have been recorded in the history table.

 rake db:migrate:history:list

Clear the history table. Useful if you want to run all your migrations again starting from version 0.

 rake db:migrate:history:clear

Initialize the history table with all the migrations defined in db/migrate up to the current database version. This is useful when adding this plugin to an existing project. This task can be run multiple times without hurting anything. This task is run automatically by the install script.

 rake db:migrate:history:init

There is currently no advanced documentation for this plugin.