class Gem::Tasks::SCM::Status

def define
  namespace :scm do
    task :status do
      if dirty?
        error "Project has uncommitted changes!"
        status
        abort
      end
    end
  end
  # alias the `validate` task to scm:status
  task :validate => 'scm:status'
end

def dirty?
  status = case @project.scm
           when :git then `git status --porcelain --untracked-files=no`
           when :hg  then `hg status --quiet`
           when :svn then `svn status --quiet`
           else            ''
           end
  return !status.chomp.empty?
end

def initialize(options={})
  super()
  yield self if block_given?
  define
end

def status
  case @project.scm
  when :git then run 'git', 'status', '--untracked-files=no'
  when :hg  then run 'hg', 'status', '--quiet'
  when :svn then run 'svn', 'status', '--quiet'
  end
end