Chris@909: Description:
Chris@909:   The plugin migration generator assists in working with schema additions 
Chris@909:   required by plugins. Instead of running migrations from plugins directly,
Chris@909:   the generator creates a regular Rails migration which will be responsible
Chris@909:   for migrating the plugins from their current version to the latest version
Chris@909:   installed.
Chris@909:   
Chris@909:   This is important because the set of application migrations remains an
Chris@909:   accurate record of the state of the database, even as plugins are installed
Chris@909:   and removed during the development process.
Chris@909: 
Chris@909: Example:
Chris@909:   ./script/generate plugin_migration [<plugin_name> <another_plugin_name> ...]
Chris@909: 
Chris@909:   This will generate:
Chris@909: 
Chris@909:     RAILS_ROOT
Chris@909:       |- db
Chris@909:           |-migrate
Chris@909:               |- xxx_plugin_migrations.rb
Chris@909: 
Chris@909:   which contains the migrations for the given plugin(s).
Chris@909:   
Chris@909:   
Chris@909: Advanced Usage:
Chris@909: 
Chris@909: There may be situations where you need *complete* control over the migrations
Chris@909: of plugins in your application, migrating a certainly plugin down to X, and
Chris@909: another plugin up to Y, where neither X or Y are the latest migrations for those
Chris@909: plugins.
Chris@909: 
Chris@909: For those unfortunate few, I have two pieces of advice:
Chris@909: 
Chris@909:  1. Why? This is a code smell [http://c2.com/xp/CodeSmell.html].
Chris@909:  
Chris@909:  2. Well, OK. Don't panic. You can completely control plugin migrations by
Chris@909:     creating your own migrations. To manually migrate a plugin to a specific
Chris@909:     version, simply use
Chris@909:     
Chris@909:       Engines.plugins[:your_plugin_name].migrate(version)
Chris@909:       
Chris@909:     where version is the integer of the migration this plugin should end
Chris@909:     up at.
Chris@909:     
Chris@909: With great power comes great responsibility. Use this wisely.