Problem while installing plugin from github

I am trying to install few plugins hosted at github to my jruby on rails
application.

I am using this command

jruby script/plugin install git://github.com/relevance/streamlined

it results in –

git: ‘init’ is not a git-command


(use ‘git help -a’ to get a list of all installed git commands)
fatal: Not a git repository: ‘.git’

I am using jruby-1.1.6RC1. I think a known problem or I am doing
something wrong.

edit:

jruby script/plugin install git://github.com/relevance/streamlined.git