Add a sync on opening the file...

[hydralien]

...by first copying to a temp file, then comparing local file with temp and then (if file are not equal) asking user whether she wants to overwrite local file. There is a config parameter sync_on_open to disable it (it's true by default - I thought of option to enable it, but then this plugin is managed manually, so it shouldn't disrupt anyone's workflow till someone deliberately pulls changes).

Generally there should be more elaborate mechanism of handling remote changes (emacs does it pretty well), but this is something to start with.

Let me know if you have any questions or need extra details.