[CMake] CMAKE_CURRENT_LIST_FILE in CMake 2.6.3

[KSpam]

My build system relies heavily on CMAKE_CURRENT_LIST_FILE.  For instance, I 
typically get a variable for the directory containing the current list file 
as follows:

get_filename_component(scriptDir ${CMAKE_CURRENT_LIST_FILE} PATH)

This has worked in prior versions of CMake; however, it does  not work in 
CMake 2.6.3 (apparently, CMAKE_CURRENT_LIST_FILE is empty).  Is this a bug, 
or is it by design?

Thanks,
Justin