Git Advanced: Monorepo, Submodules & Workflows · レッスン

Git Bisectによるデバッグ

`git bisect`を使ってバグを生み出した正確なコミットを効率的に特定し、貴重なデバッグ時間を節約します。

「Git Bisectによるデバッグ」はCoddyKit上の無料Git Advanced: Monorepo, Submodules & Workflowsレッスンです。これはレッスン2/4です。下記で完全なレッスンを無料で読むことができます。その後、ブラウザ内の組み込みコードエディタと24時間対応のAIチューターでハンズオン演習できます。これはGit Advanced: Monorepo, Submodules & Workflows学習パスの一部であり、ウェブとCoddyKitアプリ全体で進捗が同期されます。 Git Advanced: Monorepo, Submodules & Workflowsコースには全4レッスンが含まれています。

このレッスンの一部はまだ翻訳されておらず、英語で表示されています。

What is Git Bisect?

Imagine a bug appears in your project, but you're not sure which recent change caused it. Manually checking each commit can be a huge time sink!

git bisect is a powerful Git command that uses a binary search algorithm to quickly find the exact commit that introduced a bug.

The Binary Search Advantage

How does git bisect work so fast? It's like a game of 'hot or cold' with your commit history.

You tell Git a commit you know is bad (has the bug).
You tell Git a commit you know is good (before the bug existed).
Git picks a commit roughly in the middle and asks you to test it.
Based on your feedback, it halves the search space, repeating until the culprit is found.

Starting Your Bisect Hunt

To begin, first you need to tell Git you're starting a bisect session. Then, you mark the known 'bad' (buggy) commit and a known 'good' (working) commit.

You can use commit hashes, branch names, or tags.

git bisect start
git bisect bad HEAD
git bisect good <known_good_commit_hash>

The Iterative Process: Test & Mark

After you define your good and bad commits, Git will automatically check out a commit in the middle of that range. Your job is to test the code at this commit.

If the bug is present, mark it as bad.
If the bug is NOT present, mark it as good.

Git will then move to the next commit, halving the remaining search space.

Marking a Commit

Once you've tested the currently checked-out commit, use these commands to tell Git whether it's good or bad:

To mark the current commit as bad: git bisect bad
To mark the current commit as good: git bisect good

Git will then automatically check out the next commit to test.

git bisect bad
# OR
git bisect good

Narrowing Down the Problem

You'll repeat the 'test and mark' process. With each step, git bisect gets closer to the single commit that introduced the bug. It's much faster than checking commits one by one!

For a range of 100 commits, it takes at most 7 tests (log₂(100) ≈ 6.64).

Found the Culprit!

Eventually, git bisect will narrow the range down to a single commit. It will then report the first 'bad' commit found, which is your bug introducer!

After finding the bug, it's crucial to exit the bisect session to return your repository to its original state (usually the branch you were on when you started).

git bisect reset

Handling Untestable Commits

Sometimes, git bisect might land on a commit that can't be tested (e.g., it doesn't compile, or dependencies are broken). In such cases, you can tell Git to skip it:

git bisect skip

Git will then pick another commit to test, making sure to exclude the skipped one from the potential range of the bug.

git bisect skip

Automating with Git Bisect Run

For even faster debugging, you can automate the testing process using git bisect run. This command takes a script that performs the test and exits with specific codes:

0: The commit is good.
1-127 (except 125): The commit is bad.
125: The commit should be skipped (e.g., cannot build).

Git will then run the script automatically for each commit until the bug is found.

#!/bin/bash

# Example test script for git bisect run
# Replace 'make test' with your actual test command

if make test;
then
  exit 0 # Tests passed, commit is good
else
  exit 1 # Tests failed, commit is bad
fi

Bisect Workflow Check

Which of the following commands are essential when performing a manual git bisect to find a bug?

Debugging Power-Up!

You've mastered git bisect! This powerful tool transforms bug hunting from a tedious chore into an efficient, systematic process using binary search.

Start with git bisect start, defining good and bad commits.
Test and mark commits as good or bad.
Use git bisect skip for untestable commits.
Automate with git bisect run for fast, hands-free debugging.
Always finish with git bisect reset.

Happy bug hunting!

よくある質問

「Git Bisectによるデバッグ」レッスンは無料ですか？

はい。「Git Bisectによるデバッグ」の完全なテキストはこのウェブで無料で読めます。インタラクティブに演習し（組み込みコードエディタと24時間対応のAIチューター）、Git Advanced: Monorepo, Submodules & Workflowsコースの残りをアンロックするには、CoddyKit PROにアップグレードしてください。 Git Advanced: Monorepo, Submodules & Workflowsコースには全4レッスンが含まれています。

「Git Bisectによるデバッグ」で何を学びますか？

`git bisect`を使ってバグを生み出した正確なコミットを効率的に特定し、貴重なデバッグ時間を節約します。ブラウザで直接実行するハンズオンコードでGit Advanced: Monorepo, Submodules & Workflowsを演習し、24時間対応のAIチューターがレッスンを進める中での質問に答えます。

Git Advanced: Monorepo, Submodules & Workflowsを始めるのに経験は必要ですか？

事前経験は必要ありません。CoddyKitのGit Advanced: Monorepo, Submodules & Workflowsは初級者から上級者向けに構成されているため、ここから始めるか最初から始めて、自分のペースで進むことができます。これはレッスン2/4です。

「Git Bisectによるデバッグ」レッスンにはどのくらい時間がかかりますか？

ほとんどのCoddyKitレッスンは約5～10分かかります。各レッスンはコンパクトでインタラクティブなので、着実に進歩し、ウェブとアプリ全体で正確に前回の場所から再開できます。

このGit Advanced: Monorepo, Submodules & Workflowsレッスンでコードを書いて実行できますか？

はい。すべてのGit Advanced: Monorepo, Submodules & Workflowsレッスンに組み込みコードエディタが含まれているため、ブラウザでリアルコードを書いて実行し、即座のAIフィードバックを取得できます。ローカル設定は不要です。

このコースのすべてのレッスン

← Git Advanced: Monorepo, Submodules & Workflowsに戻る