Index: lib/tasks/redmine.rake
===================================================================
--- lib/tasks/redmine.rake	(révision 2280)
+++ lib/tasks/redmine.rake	(copie de travail)
@@ -79,6 +79,31 @@
       Rake::Task["db:schema:dump"].invoke
     end
 
+    desc 'Rollbacks installed plugins by 1 or many steps.'
+    task :rollback => :environment do
+      name = ENV['NAME']
+      steps = nil
+      steps_string = ENV['STEP']
+
+      if name.nil?
+        abort "The VERSION argument requires a plugin NAME."
+      end
+
+      begin
+        steps = Integer(steps_string)
+      rescue
+        abort "Invalid STEP #{steps_string} given."
+      end
+
+      begin
+        Redmine::Plugin.rollback(name, steps)
+      rescue Redmine::PluginNotFound
+        abort "Plugin #{name} was not found."
+      end
+
+      Rake::Task["db:schema:dump"].invoke
+    end
+
     desc 'Copies plugins assets into the public directory.'
     task :assets => :environment do
       name = ENV['NAME']
Index: lib/redmine/plugin.rb
===================================================================
--- lib/redmine/plugin.rb	(révision 2280)
+++ lib/redmine/plugin.rb	(copie de travail)
@@ -425,6 +425,12 @@
       Redmine::Plugin::Migrator.migrate_plugin(self, version)
     end
 
+    # Rollback this plugin to the previous version
+    def rollback(steps=1)
+      puts "Rollback #{steps} migration#{ '(s)' if steps > 1 } before (#{name})..."
+      Redmine::Plugin::Migrator.rollback_plugin(self, steps)
+    end
+
     # Migrates all plugins or a single plugin to a given version
     # Exemples:
     #   Plugin.migrate
@@ -441,6 +447,17 @@
       end
     end
 
+    # Rollbacks a single plugin by one or more step
+    # Exemples:
+    #   Plugin.rollback('sample_plugin')
+    #   Plugin.rollback('sample_plugin', 2)
+    #
+    def self.rollback(name=nil, steps=nil)
+      if name.present?
+        find(name).rollback(steps)
+      end
+    end
+
     class Migrator < ActiveRecord::Migrator
       # We need to be able to set the 'current' plugin being migrated.
       cattr_accessor :current_plugin
@@ -452,7 +469,12 @@
           return if current_version(plugin) == version
           migrate(plugin.migration_directory, version)
         end
-        
+
+        def rollback_plugin(plugin, steps=1)
+          self.current_plugin = plugin
+          rollback(plugin.migration_directory, steps)
+        end
+
         def current_version(plugin=current_plugin)
           # Delete migrations that don't match .. to_i will work because the number comes first
           ::ActiveRecord::Base.connection.select_values(