```ruby
require 'fileutils'

namespace :dm do

  task :merb_start do
    Merb.start :adapter => 'runner',
               :environment => ENV['MERB_ENV'] || 'development'
  end

  namespace :db do
    desc "Perform automigration"
    task :automigrate do
      puts '='*70
      puts "Sorry, Auto Migrations are not yet supported in DataMapper 0.9"
      puts '-'*70
      puts "They should be ready in the very near future,"
      puts "in the meantime you'll need to create your tables by hand."
      puts '='*70
    end
  end

  namespace :sessions do
    desc "Creates session migration"
    task :create => :merb_start do
      dest = File.join(Merb.root, "schema", "migrations","001_add_sessions_table.rb")
      source = File.join(File.dirname(__FILE__), "merb", "session","001_add_sessions_table.rb")
      #FileUtils.cp source, dest unless File.exists?(dest)
    end

    desc "Clears sessions"
    task :clear => :merb_start do
      table_name = ((Merb::Plugins.config[:datamapper] || {})[:session_table_name] || "sessions")
      #Merb::Orms::DataMapper.connect.execute("DELETE FROM #{table_name}")
    end
  end
end
```

Return automigration stuff to merb_datamapper rake tasks
user
```ruby
require 'fileutils'

namespace :dm do

  task :merb_start do
    Merb.start_environment :adapter => 'runner',
                           :environment => ENV['MERB_ENV'] || 'development'
  end

  namespace :db do
    desc "Perform automigration"
    task :automigrate do
      ::DataMapper.repository.auto_migrate!
    end
  end

  namespace :sessions do
    desc "Perform automigration for sessions"
    task :create => :merb_start do
      Merb::DataMapperSession.auto_migrate!
    end
   
    desc "Clears sessions"
    task :clear => :merb_start do
      table_name = ((Merb::Plugins.config[:datamapper] || {})[:session_table_name] || "sessions")
      ::DataMapper.repository.adapter.execute("DELETE FROM #{table_name}")
    end
  end
end
```
assistant