Nag based on task state before modification

With this patch, taskwarrior uses the urgency of tasks before any
modifications are applied when deciding whether to show nag messages.

Previously, taskwarrior would apply modifications before deciding
whether to show nag messages, which could lead to spurious nag messages
when completing an active task.

src/commands/CmdDone.cpp

@@ -68,11 +68,11 @@ int CmdDone::execute (std::string&)
   // Accumulated project change notifications.
   std::map <std::string, std::string> projectChanges;
 
-  Task& lowest = filtered.front();
-
   if(filtered.size() > 1) {
     feedback_affected("This command will alter {1} tasks.", filtered.size());
   }
+
+  std::vector <Task> modified;
   for (auto& task : filtered)
   {
     Task before (task);
@@ -109,11 +109,12 @@ int CmdDone::execute (std::string&)
         ++count;
         feedback_affected ("Completed task {1} '{2}'.", task);
         feedback_unblocked (task);
-        if (task.urgency () < lowest.urgency ())
-          lowest = task;
         dependencyChainOnComplete (task);
         if (Context::getContext ().verbose ("project"))
           projectChanges[task.get ("project")] = onProjectChange (task);
+
+        // Save unmodified task for potential nagging later
+        modified.push_back(before);
       }
       else
       {
@@ -133,7 +134,7 @@ int CmdDone::execute (std::string&)
     }
   }
   
-  nag(lowest);
+  nag (modified);
   
   // Now list the project changes.
   for (const auto& change : projectChanges)