我尝试使用以下命令为rails安装dynamic_form插件：
rails plugin install https://github.com/rails/dynamic_form.git
但是我收到以下错误：
/Library/Ruby/Gems/1.8/gems/railties-3.0.7/lib/rails/commands/plugin.rb:277: Commands is not a module (TypeError)
from /Library/Ruby/Gems/1.8/gems/activesupport-3.0.7/lib/active_support/dependencies.rb:239:in `require'
from /Library/Ruby/Gems/1.8/gems/activesupport-3.0.7/lib/active_support/dependencies.rb:239:in `require'
from /Library/Ruby/Gems/1.8/gems/activesupport-3.0.7/lib/active_support/dependencies.rb:225:in `load_dependency'
from /Library/Ruby/Gems/1.8/gems/activesupport-3.0.7/lib/active_support/dependencies.rb:596:in `new_constants_in'
from /Library/Ruby/Gems/1.8/gems/activesupport-3.0.7/lib/active_support/dependencies.rb:225:in `load_dependency'
from /Library/Ruby/Gems/1.8/gems/activesupport-3.0.7/lib/active_support/dependencies.rb:239:in `require'
from /Library/Ruby/Gems/1.8/gems/railties-3.0.7/lib/rails/commands.rb:17
from script/rails:6:in `require'
from script/rails:6
任何人都可以帮我这个吗？感谢。