git bisect 사용하여 버그 시작지점 검색하기

ChatGPT 4o answer

git bisect is a binary search tool built into Git that helps you quickly identify the commit that introduced a bug or regression. Instead of manually checking each commit, Git automates the search by checking commits halfway between a known good and bad commit.

🔧 Basic Workflow

Start bisect:
```
git bisect start
```
Mark the current (bad) commit:
```
git bisect bad
```
Mark a known good commit (where the bug didn't exist):
```
git bisect good <good_commit_hash>
```
Git will now checkout a commit halfway between good and bad. You test it manually:
- If the bug is present:
```
git bisect bad
```
- If the bug is not present:
```
git bisect good
```
Repeat step 4 until Git finds the exact commit that introduced the issue.
End bisecting session:
```
git bisect reset
```

🧪 Example

git bisect start
git bisect bad                # current commit has a bug
git bisect good abc1234       # abc1234 is a known good commit
# Test commit checked out by Git
git bisect bad                # if buggy
# Repeat until Git outputs:
# <bad_commit_hash> is the first bad commit
git bisect reset              # go back to original HEAD

🛠️ Bonus: Automate Testing

If you have a test script (exit code 0 = good, non-zero = bad):

git bisect run ./test-script.sh

🎯 Use Cases

Find when a bug was introduced
Detect when a performance regression happened
Discover breaking API changes in a library

Would you like an example use case applied to a real-world project?