At the point that the checksum is written, I don't think we can guarantee that all clones succeeded and that it is safe to suppress update operations in the future. ```loadTransitiveDependencies()``` would need to check for a clean exit code from each ```go get``` invocation.

It's also never safe to suppress updates when a dep is pointed at master or another branch. We could solve that by only updating repos pointed at a branch when a checksum matches perhaps.