What is the best way to sync folders?

Question

linux

There is a folder on the FTP server, you need to synchronize this folder with the local folder, but so that the differences (new files) are uploaded to a separate folder.
I used lftp with the mirror option , but in this case the folders are simply mirrored...
thanks in advance...
upd: I settled on using curlftpfs followed by a directory comparison and copying the difference... maybe it's a "collective farm" but it seems to work...

Answer 1

What about sync ? He knows how to download the difference. I used to update the local rhel6 repository at work with it.
update: rsync