pre-push hook in Git - Commands & Configuration

Introduction

Sometimes you want to check your code or run tests before sending it to a shared place. A pre-push hook is a small script that runs automatically before your code is pushed. It helps catch problems early and keeps the shared code safe.

When you want to run tests automatically before pushing code to avoid breaking the shared project.

When you want to check code style or formatting before sending your changes.

When you want to prevent pushing secrets or sensitive data by mistake.

When you want to remind yourself or your team to update documentation before pushing.

When you want to block pushes if certain conditions are not met, like commit message format.

Commands

Create a pre-push hook script that runs tests using npm before pushing code.

Terminal

echo '#!/bin/sh
npm test' > .git/hooks/pre-push

Expected Output

No output (command runs silently)

Make the pre-push hook script executable so Git can run it automatically.

Terminal

chmod +x .git/hooks/pre-push

Expected Output

No output (command runs silently)

Try to push your code to the main branch. The pre-push hook runs tests first and blocks push if tests fail.

Terminal

git push origin main

Expected Output

Running tests...

Test suite passed.

To github.com:user/repo.git

   abc1234..def5678  main -> main

Key Concept

If you remember nothing else from this pattern, remember: a pre-push hook runs a script automatically before pushing code to catch problems early.

Common Mistakes

Not making the pre-push hook script executable.

Git will not run the script if it is not executable, so the hook does nothing.

Always run chmod +x on the hook script after creating or editing it.

Writing a hook script with syntax errors or wrong commands.

The hook will fail silently or block pushes unexpectedly.

Test your hook script manually in the terminal before relying on it.

Assuming the hook runs on all machines automatically.

Hooks are local to each Git clone and are not shared by default.

Share hook scripts via a setup script or use tools like Husky for JavaScript projects.

Summary

Create a pre-push hook script inside .git/hooks/pre-push to run checks before pushing.

Make the script executable with chmod +x so Git can run it.

When you push, the hook runs automatically and can block the push if checks fail.

Practice

1. What is the main purpose of a pre-push hook in Git?

easy

A. To delete local branches after pushing

B. To merge branches automatically before pushing

C. To run checks or tests before code is pushed to a remote repository

D. To create a backup of the repository before pushing

Solution

1. Step 1: Understand the role of pre-push hooks

   Pre-push hooks run scripts before pushing code to a remote repository to catch errors early.

2. Step 2: Identify the correct purpose

   They help ensure code quality by running tests or checks before the push happens.

3. Final Answer:

   To run checks or tests before code is pushed to a remote repository -> Option C

4. Quick Check:

   Pre-push hook = run checks before push [OK]

Hint: Pre-push hooks run before push to catch problems early [OK]

Common Mistakes:

• Confusing pre-push with post-push hooks
• Thinking it merges branches automatically
• Assuming it deletes branches

2. Which of the following is the correct way to make a pre-push hook script executable on Linux or macOS?

easy

A. chmod +x .git/hooks/pre-push

B. git enable pre-push

C. chmod 777 .git/hooks/pre-push

D. git hook activate pre-push

Solution

1. Step 1: Identify how to make scripts executable

   On Linux/macOS, chmod +x sets execute permission on a file.

2. Step 2: Apply to pre-push hook

   Running chmod +x .git/hooks/pre-push makes the hook script runnable by Git.

3. Final Answer:

   chmod +x .git/hooks/pre-push -> Option A

4. Quick Check:

   Make hook executable = chmod +x [OK]

Hint: Use chmod +x to make hook scripts executable [OK]

Common Mistakes:

• Using git commands that don't exist for hooks
• Setting overly permissive permissions like 777
• Forgetting to make the script executable

3. Given this pre-push hook script snippet, what will happen if the tests fail?

#!/bin/sh
npm test || exit 1

medium

A. The push will continue regardless of test results

B. The script will delete the remote branch

C. The tests will be skipped

D. The push will be blocked and stopped

Solution

1. Step 1: Understand the script logic

   The script runs npm test. If tests fail, npm test returns non-zero, triggering exit 1.

2. Step 2: Effect of exit 1 in pre-push hook

   Exiting with a non-zero code stops the push process, blocking the push.

3. Final Answer:

   The push will be blocked and stopped -> Option D

4. Quick Check:

   Exit 1 in pre-push = block push [OK]

Hint: Exit non-zero in pre-push stops the push [OK]

Common Mistakes:

• Assuming push continues even if tests fail
• Thinking tests are skipped automatically
• Confusing exit codes with success

4. You wrote a pre-push hook script but it does not run when you push. What is the most likely cause?

medium

A. The remote repository is down

B. The script is missing execute permissions

C. You forgot to commit your changes

D. The branch name is incorrect

Solution

1. Step 1: Check script execution requirements

   Git requires hook scripts to have execute permission to run them.

2. Step 2: Identify common cause of hook not running

   If the script lacks execute permission, Git silently skips running it.

3. Final Answer:

   The script is missing execute permissions -> Option B

4. Quick Check:

   Missing execute permission = hook won't run [OK]

Hint: Check execute permission if hook doesn't run [OK]

Common Mistakes:

• Blaming remote repository for local hook issues
• Thinking commit status affects hook execution
• Assuming branch name affects hook running

5. You want your pre-push hook to run tests only on files changed in the last commit before pushing. Which approach is best?

hard

A. Use git diff --name-only HEAD~1 HEAD inside the hook to get changed files and run tests accordingly

B. Run tests on all files every time without checking changes

C. Manually list files in the hook script each time

D. Push first, then run tests on the remote repository

Solution

1. Step 1: Identify how to detect changed files

   The command git diff --name-only HEAD~1 HEAD lists files changed in the last commit.

2. Step 2: Use this command in pre-push hook

   Using this inside the hook lets you run tests only on changed files, saving time and resources.

3. Final Answer:

   Use git diff --name-only HEAD~1 HEAD inside the hook to get changed files and run tests accordingly -> Option A

4. Quick Check:

   Detect changed files with git diff for selective tests [OK]

Hint: Use git diff to find changed files for selective tests [OK]

Common Mistakes:

• Running tests on all files unnecessarily
• Manually updating file lists each time
• Running tests after push instead of before