How I used this one Git command to unblock my team

Backstory

In one of our Slack channels for work, I saw a message. The message goes something like this:

@here <project-name> is not running properly on local. Just taken a fresh pull from master and installed node_modules. [The developer attached a screenshot to the message].

~ a developer

Many developers saw the message and many developers upvoted the issue with ⬆️. There was no update. This issue was preventing my team and others from completing their assigned task. Heck, even designers were blocked because they could not do their UI/UX review. Why? Well because the issue broke the application in the Canary environment as well. Once I was done with my daily tasks and meetings, I decided to look into the issue. I was aware that to identify the problem, I'd need to check the diffs and navigate to the commit where the code was functioning correctly.

Git Command

In the quest to decipher and resolve issues within a project, a systematic approach is key. But first, let me tell you about one of the most underrated Git commands that I frequently use to investigate issues, similar to the one I encountered at work. This git command is git checkout.

git checkout <hash>

This command is an invaluable asset when troubleshooting issues. I have used this git command many times throughout my career. Below are some common scenarios for which I use this command:

• Creating a hotfix: Quickly address critical issues in the production environment by using git checkout to create a hotfix branch. This allows developers to isolate and resolve urgent problems without disrupting the main development workflow.

• Inspecting a commit: Utilize git checkout to examine the state of your project at a specific commit. This enables a detailed review of changes, helping to pinpoint when a particular modification was introduced.

• Creating a new branch: Seamlessly initiate work on a new task or feature by using git checkout -b <branch-name> to create a fresh branch. This fundamental operation ensures that development efforts remain organized, isolated, and conducive to collaborative coding practices.

• Switching between branches: Effortlessly navigate through different branches using git checkout, enabling developers to switch contexts seamlessly. Whether moving from feature development to the main branch or exploring experimental features, this command facilitates a smooth transition in the version-controlled codebase.

Investigation

Now that you know about git checkout and the the back story of the issue, let me tell you about the steps I took to resolve the issue. In the screenshot shared by the developer, the error was along the lines of Module not found: Error Can't resolve 'fs' in <path>/winston.

After reading the error message, my first thought was, "Why are we using winston on the client side?". The first thing I did was, git checkout master on my local, pulled the latest master, installed the latest packages with the command npm install and npm run dev. I was able to see the exact error.

Then on GitHub, I started looking at the diff of each commit in the master branch to see if I could find some changes related to winston. After checking some hashes, I saw that #9cc759 had some changes to do with winston. A developer had added winston logger on the client side of the application. Hence the error message, Module not found: Error Can't resolve 'fs' in <path>/winston. Then I decided to navigate to the previous git commit by using the command git checkout f600e5, followed by npm install and npm run dev.

BAM! The application was working as expected. Then I git checkout 9cc759, npm install and executed npm run dev. As expected, I saw the same exact error in the terminal.

I had found the culprit. I quickly git checkout master, removed the winston related code, npm install, and npm run dev and I did not see the error Module not found: Error Can't resolve 'fs' in <path>/winston. The application was working as expected. I pushed the code and raised the PR. I quickly notified the team in our Slack channel that I had determined the issue and shared the PR link. The PR was merged, and the team was fully unblocked.