prevent update of any object without providing the correct/current

version as part of the XML. This affects update-only at this time: 
DELETE doesn't work the same way because we don't provide the data as 
part of a DELETE

app/controllers/node_controller.rb

@@ -49,6 +49,10 @@ class NodeController < ApplicationController
     begin
       node = Node.find(params[:id])
       new_node = Node.from_xml(request.raw_post)
+      if new_node.version != node.version
+        render :text => "Version mismatch: Provided " + new_node.version.to_s + ", server had: " + node.version.to_s, :status => :bad_request
+        return
+      end  
 
       if new_node and new_node.id == node.id
         node.update_from(new_node, @user)

app/controllers/relation_controller.rb

@@ -49,6 +49,10 @@ class RelationController < ApplicationController
     begin
       relation = Relation.find(params[:id])
       new_relation = Relation.from_xml(request.raw_post)
+      if new_relation.version != relation.version
+        render :text => "Version mismatch: Provided " + new_relation.version.to_s + ", server had: " + relation.version.to_s, :status => :bad_request
+        return
+      end  
 
       if new_relation and new_relation.id == relation.id
 	relation.update_from new_relation, user

app/controllers/way_controller.rb

@@ -49,6 +49,11 @@ class WayController < ApplicationController
     begin
       way = Way.find(params[:id])
       new_way = Way.from_xml(request.raw_post)
+      if new_way.version != way.version
+        render :text => "Version mismatch: Provided " + new_way.version.to_s + ", server had: " + way.version.to_s, :status => :bad_request
+        return
+      end  
+        
 
       if new_way and new_way.id == way.id
         way.update_from(new_way, @user)