Merge pull request heavywater#14 from patcon/fnichol-13

[Issue heavywater#13] Added http_request so plugins only downloaded when updated. (

recipes/default.rb

@@ -64,6 +64,17 @@
     backup false
     owner node[:jenkins][:server][:user]
     group node[:jenkins][:server][:group]
+    action :nothing
+  end
+
+  http_request "HEAD #{node[:jenkins][:mirror]}/latest/#{name}.hpi" do
+    message ""
+    url "#{node[:jenkins][:mirror]}/latest/#{name}.hpi"
+    action :head
+    if File.exists?("#{node[:jenkins][:server][:home]}/plugins/#{name}.hpi")
+      headers "If-Modified-Since" => File.mtime("#{node[:jenkins][:server][:home]}/plugins/#{name}.hpi").httpdate
+    end
+    notifies :create, resources(:remote_file => "#{node[:jenkins][:server][:home]}/plugins/#{name}.hpi"), :immediately
   end
 end