You’ve completed the feature or fixed the bug, written a few unit tests, polished the format and comments. Now it’s time to commit the change…
You gotta diff that puppy! Any source code management system will let you review the differences between your branch and the existing code.
Never merge/check in without a diff. It’s easy to overlook this simple step, but trust me, you may be surprised at the cruft — false steps, debug prints, etc. — that your are about put into “master”.
People who review your code will be looking at the diffs. You owe it to them and yourself to take that step first.