Bisect: Hunting Down Bad Commits
Use git bisect to perform a binary search through history and pinpoint the exact commit that introduced a bug, even across hundreds of commits.
Bisect: Hunting Down Bad Commits is a free Git Advanced: Monorepo, Submodules & Workflows lesson on CoddyKit — lesson 4 of 4. You can read the complete lesson below for free — then practise it hands-on in the browser with a built-in code editor and a 24/7 AI tutor. It is part of the Git Advanced: Monorepo, Submodules & Workflows learning path, one of 4 lessons in the course, and your progress syncs across the web and the CoddyKit app.
The Needle in the Haystack
A bug hides somewhere in your last 200 commits. git bisect runs a binary search through history, halving the suspect range with each test.
How Binary Search Helps
Checking 200 commits linearly means 200 tests. Binary search needs only about log2(200) ≈ 8 — bisect narrows the culprit dramatically faster.
Starting a Bisect
Kick off a session with git bisect start. From there Git walks you through marking commits as good or bad.
git bisect startMarking Good and Bad
Tell Git where the bug exists (bad) and an older commit where it didn't (good). That bounds the search range.
git bisect bad HEAD
git bisect good v1.2.0Testing Each Checkout
Git checks out the midpoint commit. You test it and report good or bad, and Git picks the next midpoint accordingly.
git bisect good
# or
git bisect badReaching the Culprit
After a few rounds, Git names the first bad commit — its hash, author, and message — the exact change that introduced the bug.
Ending the Session
Always finish with git bisect reset. It returns you to your starting branch and clears the bisect state.
git bisect resetAutomating with a Script
If you can test the bug programmatically, git bisect run ./test.sh automates the whole search — exit 0 means good, non-zero means bad.
git bisect run ./test.shThe Skip Escape Hatch
Hit a commit you can't test (it won't build)? git bisect skip tells Git to try a nearby commit instead.
git bisect skipReviewing the Log
git bisect log saves or replays the decisions you made — useful for documenting how you found a bug or resuming a session later.
git bisect logBest Practices
For reliable bisects: have a clear, reproducible test, keep commits small and atomic, and automate with git bisect run whenever you can.
Quick Check
Test your bisect knowledge.
Recap
Recap: git bisect start, mark good and bad, test each midpoint to halve the range, automate with run, skip the untestable, and reset when done.
Frequently asked questions
Is the “Bisect: Hunting Down Bad Commits” lesson free?
Yes — the full text of “Bisect: Hunting Down Bad Commits” is free to read here on the web, and the Git Advanced: Monorepo, Submodules & Workflows course includes 4 lessons in total. To practise it interactively (a built-in code editor and a 24/7 AI tutor) and unlock the rest of the Git Advanced: Monorepo, Submodules & Workflows course, upgrade to CoddyKit PRO.
What will I learn in “Bisect: Hunting Down Bad Commits”?
Use git bisect to perform a binary search through history and pinpoint the exact commit that introduced a bug, even across hundreds of commits. You practise Git Advanced: Monorepo, Submodules & Workflows with hands-on code you run directly in the browser, and a 24/7 AI tutor answers your questions as you work through the lesson.
Do I need any experience to start Git Advanced: Monorepo, Submodules & Workflows?
No prior experience is required. Git Advanced: Monorepo, Submodules & Workflows on CoddyKit is structured for beginners through advanced learners; this is — lesson 4 of 4, so you can start here or from the beginning and move at your own pace.
How long does the “Bisect: Hunting Down Bad Commits” lesson take?
Most CoddyKit lessons take about 5–10 minutes. Each one is bite-sized and interactive, so you make steady progress and pick up exactly where you left off across the web and the app.
Can I write and run code in this Git Advanced: Monorepo, Submodules & Workflows lesson?
Yes. Every Git Advanced: Monorepo, Submodules & Workflows lesson includes a built-in code editor, so you write and run real code right in your browser and get instant AI feedback — no local setup required.
All lessons in this course
- Interactive Rebase and Amending
- Stashing and Cherry-picking Changes
- Reflog for Recovery
- Bisect: Hunting Down Bad Commits