Client-side vs server-side hooks in Git - When to Use Which

The Big Idea

What if your project could catch mistakes before they cause headaches for everyone?

The Scenario

Imagine you and your friends are working on a shared project. Every time someone makes a change, they have to remember to check if their code follows the rules before sharing it. Sometimes they forget, and mistakes sneak in.

The Problem

Relying on everyone to manually check their work is slow and risky. Mistakes can break the project, and fixing them later wastes time and causes frustration.

The Solution

Client-side and server-side hooks automatically check and enforce rules at different stages. Client-side hooks catch issues before changes leave your computer, while server-side hooks protect the shared project by checking changes before they are accepted.

Before vs After

✗ Before

Remember to run tests and style checks before commit

✓ After

Use a client-side hook to run tests automatically before commit

What It Enables

This makes teamwork smoother and safer by catching problems early and keeping the shared project healthy.

Real Life Example

A developer tries to commit code with a typo. The client-side hook stops the commit and asks to fix it. Another developer pushes code to the server, but the server-side hook rejects it because tests fail, preventing broken code from entering the project.

Key Takeaways

Manual checks are slow and error-prone.

Client-side hooks catch problems before code leaves your computer.

Server-side hooks protect the shared project by validating incoming changes.

Practice

1. Which of the following best describes a client-side Git hook?

easy

A. A Git command to clone repositories.

B. A script that runs on the Git server to control repository access.

C. A tool to merge branches automatically on the server.

D. A script that runs on your local machine before or after Git actions like commit or push.

Solution

1. Step 1: Understand client-side hooks context

   Client-side hooks run on your local computer and trigger before or after Git commands like commit or push.

2. Step 2: Differentiate from server-side hooks

   Server-side hooks run on the Git server to enforce rules for all users, unlike client-side hooks which are local.

3. Final Answer:

   A script that runs on your local machine before or after Git actions like commit or push. -> Option D

4. Quick Check:

   Client-side hook = local script [OK]

Hint: Client-side hooks run locally before/after Git commands [OK]

Common Mistakes:

• Confusing client-side hooks with server-side hooks
• Thinking hooks run only on the server
• Assuming hooks are Git commands

2. Which of the following is the correct location to place a client-side pre-commit hook script in a Git repository?

easy

A. /usr/local/git/hooks/pre-commit

B. .git/hooks/server-pre-commit

C. .git/hooks/pre-commit

D. .git/pre-commit

Solution

1. Step 1: Identify the standard hooks directory

   Git client-side hooks are stored inside the .git/hooks directory of the local repository.

2. Step 2: Confirm the correct hook filename

   The pre-commit hook script must be named exactly 'pre-commit' inside .git/hooks.

3. Final Answer:

   .git/hooks/pre-commit -> Option C

4. Quick Check:

   Client-side hooks live in .git/hooks [OK]

Hint: Client-side hooks go in .git/hooks folder [OK]

Common Mistakes:

• Placing hooks outside the .git directory
• Using wrong filenames for hooks
• Confusing server-side hook locations

3. Given this server-side hook script named pre-receive on the Git server:

#!/bin/sh
while read oldrev newrev refname
 do
   if [ "$refname" = "refs/heads/main" ]; then
     echo "Pushes to main branch are not allowed."
     exit 1
   fi
 done
exit 0

What will happen if a user tries to push commits to the main branch?

medium

A. The push will be rejected with the message 'Pushes to main branch are not allowed.'

B. The push will succeed without any message.

C. The push will be accepted but with a warning.

D. The server will crash due to a syntax error.

Solution

1. Step 1: Analyze the pre-receive hook logic

   The script reads each ref being pushed. If the ref is 'refs/heads/main', it prints a message and exits with status 1, which rejects the push.

2. Step 2: Understand Git hook exit codes

   Exiting with 1 means failure, so Git rejects the push and shows the message to the user.

3. Final Answer:

   The push will be rejected with the message 'Pushes to main branch are not allowed.' -> Option A

4. Quick Check:

   Exit 1 in server hook rejects push [OK]

Hint: Exit code 1 in server hook blocks push [OK]

Common Mistakes:

• Assuming push succeeds despite exit 1
• Confusing client-side and server-side hook effects
• Ignoring the printed message

4. You wrote a client-side pre-commit hook script but it does not run when you commit. What is the most likely reason?

medium

A. The script is placed in the wrong directory on the server.

B. The script file is not executable.

C. Git does not support pre-commit hooks.

D. You forgot to push the hook to the remote repository.

Solution

1. Step 1: Check script permissions

   Client-side hooks must be executable files. If not, Git will ignore them silently.

2. Step 2: Verify hook location and Git support

   The hook must be in .git/hooks locally. Git supports pre-commit hooks, and pushing hooks to remote does not affect local hooks.

3. Final Answer:

   The script file is not executable. -> Option B

4. Quick Check:

   Hooks must be executable to run [OK]

Hint: Make hook scripts executable with chmod +x [OK]

Common Mistakes:

• Placing hooks on the server for client-side use
• Thinking Git lacks pre-commit hooks
• Expecting hooks to transfer via git push

5. You want to enforce that all commits pushed to the shared repository have a signed commit message. Which hook setup is best to ensure this rule is always checked regardless of the user's local setup?

hard

A. Implement a server-side pre-receive hook that rejects unsigned commits.

B. Ask each developer to add a client-side commit-msg hook to check signatures.

C. Use a client-side pre-push hook to warn about unsigned commits.

D. Rely on GitHub or GitLab UI to manually check commit signatures.

Solution

1. Step 1: Understand enforcement scope

   Client-side hooks depend on each user's setup and can be bypassed or missing.

2. Step 2: Use server-side hooks for mandatory checks

   Server-side hooks run on the shared repository and can reject pushes that don't meet rules, ensuring enforcement for all users.

3. Final Answer:

   Implement a server-side pre-receive hook that rejects unsigned commits. -> Option A

4. Quick Check:

   Server hooks enforce rules for all pushes [OK]

Hint: Use server-side hooks to enforce rules for all users [OK]

Common Mistakes:

• Relying only on client-side hooks for enforcement
• Assuming UI checks block pushes automatically
• Ignoring that client hooks can be disabled