Doesn't work offline

[rickb777]

If I am working offline, I would expect to be able to trace back through previous history, even though I cannot fetch new deps from the internet.

This doesn't work because git fetch --ff-only is executed and if this fails, the sync fails.

However, the failure condition should be more nuanced. If the git fetch and the git checkout both fail, then glock should abort. But if the checkout succeeds, then the sync should proceed anyway.