task(name).clear clears description/comment

The test_clear_comments test case is due to David Chelimsky
(#88).

lib/rake/task.rb

@@ -123,6 +123,7 @@ def reenable
     def clear
       clear_prerequisites
       clear_actions
+      clear_comments
       self
     end
 
@@ -138,6 +139,13 @@ def clear_actions
       self
     end
 
+    # Clear the existing comments on a rake task.
+    def clear_comments
+      @full_comment = nil
+      @comment = nil
+      self
+    end
+
     # Invoke the task if it is needed.  Prerequisites are invoked first.
     def invoke(*args)
       task_args = TaskArguments.new(arg_names, args)

test/test_rake_task.rb

@@ -104,10 +104,12 @@ def test_can_double_invoke_with_reenable
   end
 
   def test_clear
+    desc "a task"
     t = task("t" => "a") { }
     t.clear
     assert t.prerequisites.empty?, "prerequisites should be empty"
     assert t.actions.empty?, "actions should be empty"
+    assert_nil t.comment, "comments should be empty"
   end
 
   def test_clear_prerequisites
@@ -123,6 +125,20 @@ def test_clear_actions
     assert t.actions.empty?, "actions should be empty"
   end
 
+  def test_clear_comments
+    desc "the original foo"
+    task :foo do
+    end
+
+    task(:foo).clear_comments
+
+    desc "a slightly different foo"
+    task :foo do
+    end
+
+    assert_equal "a slightly different foo", task(:foo).comment
+  end
+
   def test_find
     task :tfind
     assert_equal "tfind", Task[:tfind].name