How to merge folders and subfolders?
Solution 1:
Try:
rsync -aP /ORIGINAL_A/* /DESTINATION_C/
This is like a copy of the folder A
rsync -aP /ORIGINAL_B/* /DESTINATION_C/
That should sync the folders A an B to another the new folder C.
You could sync the file from A to B directly but you don't will have data loss this way.