Folderslave option

The foldermaster feature is useful but it does not allow several machines to receive updates from each other while other “unreliable” machines may receive updates without being able to change files on the “reliable” machines. How about adding an option for Folderslave meaning that the folder can receive changes but not send them?

This feature has been requested several times before; e.g.:

and has an issue on github:

I don’t know the current status of the implementation though.