for normal requests to /login, save the referrer and redir back there

properly closes #164

app/controllers/login_controller.rb

@@ -11,6 +11,7 @@ class LoginController < ApplicationController
 
   def index
     @title = "Login"
+    @referer ||= request.referer
     render :action => "index"
   end
 
@@ -28,12 +29,22 @@ class LoginController < ApplicationController
       if (rd = session[:redirect_to]).present?
         session.delete(:redirect_to)
         return redirect_to rd
-      else
-        return redirect_to "/"
+      elsif params[:referer].present?
+        begin
+          ru = URI.parse(params[:referer])
+          if ru.host == Rails.application.domain
+            return redirect_to ru.to_s
+          end
+        rescue => e
+          Rails.logger.error "error parsing referer: #{e}"
+        end
       end
+
+      return redirect_to "/"
     end
 
     flash.now[:error] = "Invalid e-mail address and/or password."
+    @referer = params[:referer]
     index
   end
 

app/views/login/index.html.erb

@@ -29,5 +29,9 @@
     ask them for an invitation or <a href="/invitations/request">request one
     publicly</a>.
     </p>
+
+    <% if @referer.present? %>
+      <%= hidden_field_tag :referer, @referer %>
+    <% end %>
   <% end %>
 </div>