move use of contextTask out of columns, into commands

src/commands/CmdAdd.cpp

@@ -30,6 +30,8 @@
 #include <format.h>
 #include <main.h>
 
+extern Task* contextTask;
+
 ////////////////////////////////////////////////////////////////////////////////
 CmdAdd::CmdAdd ()
 {
@@ -51,6 +53,10 @@ int CmdAdd::execute (std::string& output)
 {
   // Apply the command line modifications to the new task.
   Task task;
+
+  // the task is empty, but DOM references can refer to earlier parts of the
+  // command line, e.g., `task add due:20110101 wait:due`.
+  contextTask = &task;
   task.modify (Task::modReplace, true);
   Context::getContext ().tdb2.add (task);