Feature - #156

+ Task now supports both a 'side' and 'diff' style of undo.
+ Undo now observes the 'color.undo.before' and 'color.undo.after'
  configuration variables.

src/Att.cpp

@@ -50,6 +50,7 @@ static const char* internalNames[] =
   "limit",
   "status",
   "description",
+  // Note that annotations are not listed.
 };
 
 static const char* modifiableNames[] =
@@ -758,6 +759,19 @@ int Att::value_int () const
   return atoi (mValue.c_str ());
 }
 
+////////////////////////////////////////////////////////////////////////////////
+void Att::allNames (std::vector <std::string>& all)
+{
+  all.clear ();
+
+  unsigned int i;
+  for (i = 0; i < NUM_INTERNAL_NAMES; ++i)
+    all.push_back (internalNames[i]);
+
+  for (i = 0; i < NUM_MODIFIABLE_NAMES; ++i)
+    all.push_back (modifiableNames[i]);
+}
+
 ////////////////////////////////////////////////////////////////////////////////
 void Att::value_int (int value)
 {