Generally Googlers edited and reviewed a changelist (which is like amending a commit that hasn't been pushed yet) and then submitted when it's considered ready

Generally Googlers edited and reviewed a changelist (which is like amending a commit that hasn't been pushed yet) and then submitted when it's considered ready to deploy. You're expected to run your project's test targets (which might include a few critical dependents) before you submit, but if you have a huge set of dependents there's no way to be certain none will break—their tests might be flaky or fail for reasons that aren't your fault, and there will be hundreds of new changelists submitted (including changes to your own dependencies!) while your tests were running.