handling to prevent nested shares needs improvement, client visibility

While setting up test scenarios yesterday, I attempted to create shares for two folders under my ~/Documents folder.

As it turns out, I had a share for all of ~/Documents from one test system in the past, though no current clients were syncing from it.

The client quite correctly detects that this would set up a nested situation and blocks it.

The problem is, it blocks it with errors deep in the logs. There's no indication in Nautilus that this is an invalid scenario. The user simply selects "sync to Ubuntuone" on the context menu, and nothing ever happens (from his viewpoint).

I'm not sure the best place to handle this. One method would be to disable the menu item for paths that are beneath known share paths (we know this locally because it's displayed in the control panel).