It hasn't been an issue in my experience at $DAY_JOB, but for us all commits must pass CI and not just the tip of whatever branch was just pushed. So branches with partial commits that fail CI cannot be merged. So if you commit an incorrect partial commit, you either squash it into a commit that does pass CI (usually the next one forward) or you rebase and edit the failed commit and fix it and force push your branch and run CI on the whole changeset again.