I\'m using MacFusion with OSXFuse(similar to MacFuse) to mount my server over SSH onto my office machine. When I cd into my rails work directory on the server, i can\'t see any
Are you ssh'ing to a directory that's inside your work tree? If the root of your ssh mount point doesn't include the .git dir, then zsh won't be able to find git info. Make sure you're mounting something that includes the root of the repo.
As for GIT_DISCOVERY_ACROSS_FILESYSTEM, it doesn't do what you want. Git by default will stop at a filesystem boundary. If you turn that on (and it's just an env var), then git will cross the filesystem boundary and keep looking. However, that's almost never useful, because you'd be implying that you have a .git directory on your local machine that's somehow meant to manage a work tree that's comprised partially of an sshfs mount. That doesn't make much sense.