FolderSync is a commandline application that maintains backups of a folder automatically. It will update the contents of the backups on update of the primary.
Use the following steps to clone and run FolderSync
git clone https://github.com/keshav11/FolderSync.git
cd FolderSync
ant compile
cd out
java foldersync.FolderSync path_to_folder1 path_to_folder2