This ensures that any non-colliding changes pushed upstream within the few minute
window that smoke tests were running will not break the `git push`. While we do make
the assumption that tests still pass after this, breaking changes from automated
diffs should be exceedingly rare. For human-authored changes, we have a land queue to
help mitigate this.
This is copied from `automated-commits.sh` to bring this script up to
par with the sanity checking we already do there. The next step is to cleanup
`automated-commits.sh` so that it calls `land-patch.sh` directly.
Depends on D7467