Suppose I have some network-accessible storage, like an NFS mount, google-drive-ocamlfuse mount or SSHFS. These are all immediate mode storage systems, i.e. when I copy a file to the mount, it is immediately uploaded, and the operation blocks until the upload is finished. Similarly for downloading, files have to always be re-downloaded on opening.
I'm looking for a program which would, given a directory on a local filesystem, synchronize it with the above mentioned storage in background. To the user this program with such storage should look very similar to Dropbox: put a file in the directory — and it gets uploaded in background, something changed on the remote storage — and soon you have the change reflected in you local directory.
Is there such a (freeware) program? I'd prefer opensource one.