On PCs there is a function that allows you to sync something on your PC to an external disk every time you plug the drive in. Has anyone seen software like that for the Mac? I have "File Synchronization", but looking for something with more automatic functionality like mentioned above.
To see what it's doing add --verbose, to see what it would do, without doing it, also add --dry-run
It'll only copy the parts of the files that are needed.
To do a two way sync you need some more of the options and really understand the impact of what you do. Esp deleting files is tricky as you need to decide if a file is either deleted, or either added on the other store.
Hence to do a full two way sync with deletes requires stats to be kept to at least determine the time it was last run and clocks being set appropriately. Still, a simple script could achieve it.