Run a one-way sync with delete from the command-line?

I have lots of pairs of folders that I regularly sync using DO, some on my local network and some to remote FTP servers. Sync is a great feature, and in every case I want to do a one-way sync that makes the destination folder end up exactly like the source folder by doing three things: (1) copying files that don't exist in the destination, (2) updating files that do, and (3) deleting files in the destination that don't exist in the source.

I see the internal COPY command has the ability to do a limited version of the sync, accomplishing (1) and (2) from my list above but it seems not (3). I've put up with having to invoke multiple sets of folder syncs manually for quite some time, but now the list is getting lengthy enough that it's onerous. Is there some way to run a one-way sync with delete from the command-line? Thanks in advance.

I am afraid there is not.

Syncthing might be a better tool for the job:

If you want an Opus solution, you could use a modified version of this script

to delete the superfluous files or even handle the entire synchronization.