Version Control

The test suite has been green for three weeks. Today npm test fails on an assertion that has nothing to do with what you just changed, and git log v1.4.0..HEAD shows 340 commits from four people since the last release anyone is sure worked. Reading every diff costs you a day. Checking out commits at random is faster and still not a plan. git bisect turns that into a binary search. You give it one commit you know is good and one you know is bad; it checks out the commit halfway between them and waits while you test that single commit and report back. Each answer halves the range. 340 commits resolve in at most 9 tests, since 2^9 = 512. ...

You pull the latest main and Git stops with CONFLICT (content): Merge conflict in checkout.js. You resolve it, and the log now shows a commit called Merge branch 'main' into feature/checkout sitting on top of the three commits you actually wrote. Four commits, one real change. A teammate reading that history next month can’t tell which is which. git merge and git rebase both answer the same question: how do I bring my branch up to date with changes made elsewhere. They leave very different traces behind, and picking the wrong one on a shared branch causes real damage. ...