This used to be done manually via "gcheckout" but that's long since been replaced. Users now don't do anything but create quick throwaway clients that have the

This used to be done manually via "gcheckout" but that's long since been replaced. Users now don't do anything but create quick throwaway clients that have the entire repo in view. Until very recently there was a versioning system for core libraries so those wouldn't typically be at HEAD (minimizing global breakage). Even that has been eliminated now and it's truly just the presubmit checks and code review process that keeps things sane.