You can also use the placeholder $(APIVersion) in the manifest tx file to load different filenames for the different APIversions (live, pts).
Example:
Code:
source_$(APIVersion).lua
This will load the file source_100024.lua on live and source_100025.lua on PTS.
Be sure to always load a "fallback" version before so if the API changes one day and your addon is missing the file, your addon won't break!