Git- Debugging

Debugging is an important part of software development, and Git provides powerful tools to help with this process. One such tool is git bisect, which allows developers to efficiently identify the commit that introduced a bug by performing a binary search through the project’s history. This guide will explain how to use git bisect for effective debugging, enhancing your ability to maintain a clean and stable codebase.

What is Git Bisect?

Git bisect is a Git command that helps you find the exact commit that introduced a bug or issue. It leverages a binary search algorithm to narrow down the range of commits, making the debugging process faster and more efficient. By marking commits as "good" or "bad," Git systematically eliminates half of the remaining commits with each step until the problematic commit is identified.

Why Use Git Bisect?

Here are some reasons why git bisect is an essential tool for debugging:

• Efficiency: Quickly narrows down the problematic commit, saving time compared to manually checking each commit.
• Precision: Accurately identifies the commit that introduced the bug, making it easier to understand and fix the issue.
• Automation: Can be automated with scripts for consistent testing, reducing the likelihood of human error.

How Does Git Bisect Work

Here’s a simple breakdown of how git bisect works:

• Start the Bisecting Process:
  • Use git bisect start to begin the search.
• Mark the Bad Commit:
  • Run git bisect bad to mark the commit where the bug appeared.
• Mark the Good Commit:
  • Use git bisect good to mark a commit where everything was working fine.
• Git Finds the Middle Commit:
  • Git will automatically check the middle commit and tell you if it’s "good" or "bad." This process continues until the exact commit causing the bug is identified.

After the following set of commands, git selects the commit in the middle range, checks it and return output.

Note: In this image, we have not mentioned any version of git bisect bad and git bisect good, so when we don't mention any version, the current version is taken by default.

Key Git Bisect Commands

• git bisect reset: After finding the bug, use this command to return to the original state and stop the bisect process.
• 
• To undo the change of state: Sometimes, rather than finding a bug in commit bisect command it can also be used to switch the previous state. So it can be used when we are looking to commit that caused a change between "old" and "new" state. How it works? Instead of bad and good, old and new are used respectively.
  • git bisect start
  • git bisect old "revision"
  • git bisect new "revision"
• git bisect log: After good and bad revisons, this command is used to get overview of the work done.
• git bisect skip "version1".."version2": It is used to skip a range of commits. It implies no commit ranging from version1 upto version2 should be tested.

Additional Git Troubleshooting Tips

Apart from git bisect, Git offers several other tools to troubleshoot and fix issues:

1. Broken Pipe Errors on git push

If you encounter "Write failed: Broken pipe" errors during a push operation:

• Increase the http.postBuffer size by running:
  git config http.postBuffer 524288000
• Repack your repository with:
  git repack

2. ssh_exchange_identification Error

This error happens when too many unauthenticated SSH attempts are made. To resolve it:

• Increase the MaxStartups limit in /etc/ssh/sshd_config.

3. Timeouts on git push/git pull

If these commands are taking too long, check your network connection. You may also use traceroute to diagnose any network issues.

4. Error: transfer closed with outstanding read data remaining

This typically occurs when working with large repositories. To solve this:

• Use Git LFS (Large File Storage) to handle large files efficiently.

Using Git Clean to Manage Untracked Files

The git clean command is used to delete untracked files from git project. This command completely removes files from the working tree and cannot be recovered again. So this command should be carefully used.

git clean options:

• -n or --dry-run This command does not remove files, but it is a dummy command which tells what would be actually done. It is used to test run.
• -f or --force This command remove files from the current directory. This is a necessary command unless clean.requireforce configuration is set to false.
• -d This command removes untracked directories along with untracked files.
• -i or --interactive As the name suggests, it is an interactive command that tells what has to be done.

Interactive Mode:

In interactive mode, you can choose which untracked files or directories to delete. You can filter files by pattern, select multiple files to delete, or even exit without deleting any files.

• clean: This command deletes untracked directories/files at the point.
• filter by pattern: We can input a pattern such as *_ to exclude files/directories from deletion. For eg: "*.py" will exclude mentioned file extension from deletion.
• select number: This command allot a number to untracked files/directories to be deleted. We can also make multiple selection. For Example:
  • "3-5" deletes file number "3, 4, 5".
  • "3-5, 8, 9" deletes "3, 4, 5, 8, 9".
  • "3-" deletes file numbers starting from 3 to the last file number.
  • "*" deletes everything.
• ask each: This will ask one by one to delete the particular file or not.
• quit: This option lets you to exit without deleting.

Conclusion

Git debugging is a crucial aspect of software development, and mastering tools like git bisect can significantly enhance your debugging workflow. With git bisect, you can efficiently identify problematic commits using a binary search, saving time and improving precision. Additionally, Git’s troubleshooting commands like git clean, git push errors, and git pull timeouts provide powerful solutions to common issues. By learning these Git tools, developers can maintain clean, error-free codebases, ensuring smooth version control and faster development cycles. Git debugging, Git troubleshooting tools, and Git bisect are indispensable for improving software quality and boosting productivity, making them essential for developers looking to streamline their Git workflow and resolve issues with ease.