Don't send JOIN messages twice if a user is already present. Fixes ze…

…rowidthgh-4.

As a side effect, this prevents a bug wherein an existing CamperVan::User was
being created with a CamperVan::User as the source rather than a FireRing::User,
causing a crash.

lib/camper_van/channel.rb

@@ -297,8 +297,10 @@ def map_message_to_irc(message)
           end
 
         when "Enter"
-          client.campfire_reply :join, name, channel
-          users[user.id] = User.new(user)
+          unless users[user.id]
+            client.campfire_reply :join, name, channel
+            users[user.id] = User.new(user)
+          end
 
         when "Leave", "Kick" # kick is used for idle timeouts
           client.campfire_reply :part, name, channel, "Leaving..."

spec/camper_van/channel_spec.rb

@@ -403,6 +403,14 @@ def msg(type, attributes={})
       @client.sent.last.must_match %r/:joe\S+ JOIN #test/
     end
 
+    it "does not resend a join command when a user enters the room twice" do
+      @channel.map_message_to_irc msg("Enter")
+      @client.sent.clear
+      @client.sent.last.must_equal nil
+      @channel.map_message_to_irc msg("Enter")
+      @client.sent.last.must_equal nil
+    end
+
     it "adds the user to the internal tracking list when a user joins" do
       @channel.map_message_to_irc msg("Enter")
       @client.sent.last.must_match %r/:joe\S+ JOIN #test/