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Git hooks — The unsung rescuers

What a git hook can do is constrained only by the developer’s imagination. Git hooks are one of the most productive hacks every software engineering team must possess.

First things first:

I assume the reader has some hands on experience with git and basic shell scripting. We will be going through only two types of git hooks in this write out. The intention is to introduced the reader to git hooks,not to explain details of different types of git hooks.

The need:

Keeping the application’s build pipeline always green is a skill. We all often see developers saying :

“oh! the pull request build failed because of failing unit tests or integration tests”.

“Ahh !! damn I have push the data base password into git.”

On a sincere note, committing passwords into git is a crime that a developer can potentially do unknowingly. I once read about a situation where a developer has committed the passwords of AWS instance which were eventually taken over by a hacker and whole AWS was compromised for the organization and used to mine cryptocurrency for 24hrs. We can stop this using a pre-commit git hook.

To fix the above scenarios developers have to revert that commit or push a new commit with fixed test suite or by removing the password that is pushed. This eventually disturbs the commit history of the application.And yes, there is a difference between a developer and a good developer. We can be good developers. We can handle these types of common mistakes even before we commit the code into our local machines.

Dive in:

We will be going through pre-commit hook and pre-push hooks only in this write out. If you are interested in knowing more about different types of git hooks, refer this link.

A pre-commit hook script will be executed every time you commit the code in to the local machine where as a pre-push hook script will be executed every time you push the code to git.

Pre-commit hook to detect passwords in staged files:

<script src=”https://gist.github.com/akhil-ghatiki/944db313e1fafa66d11c3f189b15eb1e.js"></script>

We are using a regex here to detect any line of the type password:<<text>> in the staged files. (One needs to change this regex according to how passwords go into your code.)

Pre-commit hook to abort commit for failing unit tests:

<script src=”https://gist.github.com/akhil-ghatiki/6ec1e96ec289ff37d861fed823afd560.js"></script>

Of course, both the above implementations can go into one pre-commit git hook. Save the above file as pre-commit.sh

Pre-push hook to abort pushing for failing integration tests:

<script src=”https://gist.github.com/akhil-ghatiki/16ac55b276d6fb42d3f563db6a235dea.js"></script>

Save the above file as pre-push.sh

Save these files in a folder “githooks” and run the below commands. So that any further changes can be made in these files and they will reflect in the git’s hooks.

ln -s -f /Users/<<Path to your project folder>>/githooks/pre-commit ./.git/hooks/pre-commit
ln -s -f /Users/<<Path to your project folder>>/githooks/pre-push ./.git/hooks/pre-push

God Speed !!!!