bisect

Detailed Explanation

1. Starting Bisect: You start the bisect process by specifying a known good commit and a known bad commit. Git will then check out a commit in the middle of the range.

2. Marking Commits: You mark each commit as good or bad using git bisect good and git bisect bad. Based on your input, Git will narrow down the range of commits to find the exact commit that introduced the bug.

3. Automating Bisect: You can automate the bisect process by providing a script that tests for the bug. Git will run the script at each step and mark the commit as good or bad based on the script's exit status.

4. Ending Bisect: Once the offending commit is found, you end the bisect process using git bisect reset, which returns your repository to its original state.

Examples

1. Starting Bisect:

   git bisect start git bisect bad HEAD git bisect good v1.0

   This starts the bisect process with the current commit marked as bad and the v1.0 tag marked as good.

2. Marking a Commit as Good:

   git bisect good

   This marks the current commit as good, indicating that the bug was not present in this commit.

3. Marking a Commit as Bad:

   git bisect bad

   This marks the current commit as bad, indicating that the bug is present in this commit.

4. Automating Bisect with a Script:

   git bisect start git bisect bad HEAD git bisect good v1.0 git bisect run ./test-script.sh

   This starts the bisect process and uses ./test-script.sh to automatically test each commit. The script should exit with status 0 if the commit is good and non-zero if the commit is bad.

Common use cases

Common use cases for the git bisect command include:

1. Identifying the Commit that Introduced a Bug: When a bug is discovered, git bisect can help pinpoint the exact commit that introduced the bug by performing a binary search through the commit history.

2. Finding Performance Regressions: If a performance issue is detected, git bisect can be used to find the commit that caused the regression by testing the performance at each step.

3. Locating the Source of a Test Failure: When a test starts failing, git bisect can help identify the commit that caused the test to fail, making it easier to understand and fix the issue.

4. Debugging Complex Codebases: In large repositories with many commits, git bisect can efficiently narrow down the range of commits to find the one responsible for a problem, saving time and effort compared to manually checking each commit.