post-merge hook in Git - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a post-merge hook in Git?

A post-merge hook is a script that runs automatically after a successful git merge. It helps automate tasks like updating dependencies or cleaning up files.

beginner

Where do you place the post-merge hook script in a Git repository?

You place the post-merge script inside the .git/hooks/ directory of your repository, and make sure it is executable.

beginner

What file permissions should a post-merge hook script have?

The post-merge hook script should have executable permissions, usually set with chmod +x post-merge.

beginner

Give an example of a simple post-merge hook script that prints a message.

A simple post-merge script in Bash:

#!/bin/sh
echo "Merge completed successfully!"

beginner

Why use a post-merge hook instead of running commands manually after merging?

Using a post-merge hook automates repetitive tasks, reduces human error, and ensures important steps run every time a merge happens.

What triggers the post-merge hook in Git?

A After pushing to remote

B Before a git commit

C When cloning a repository

D After a successful git merge

The post-merge hook runs automatically right after a successful git merge.

Where should the post-merge hook script be located?

A Inside the .git/hooks directory

B In the root project directory

C In the user's home directory

D In the remote repository

Git looks for hook scripts inside the .git/hooks directory of the local repository.

Which command makes a post-merge hook script executable?

A chmod +x post-merge

B git enable post-merge

C chmod 644 post-merge

D git hook activate post-merge

You use chmod +x to give execute permission to the hook script.

What is a common use of a post-merge hook?

A To create a new branch

B To update dependencies after merging

C To push changes to remote

D To delete the repository

A post-merge hook often runs commands like updating dependencies or rebuilding files after a merge.

Can the post-merge hook run on a remote server automatically?

A Only if configured in the remote repo

B Yes, always on remote servers

C No, it runs only on the local machine

D Only during git push

Git hooks like post-merge run only on the local machine where the merge happens.

Explain what a post-merge hook is and describe a simple task it can automate.

Think about what happens right after you combine code changes.

Describe how to set up a post-merge hook script in a Git repository.

Focus on where the script goes and what permissions it needs.

Practice

1. What is the main purpose of the post-merge hook in Git?

easy

A. To create a new branch after merging

B. To prevent merges from happening

C. To delete merged branches automatically

D. To run commands automatically after a merge completes

Solution

1. Step 1: Understand the role of Git hooks

   Git hooks are scripts that run at specific points in Git workflows to automate tasks.

2. Step 2: Identify the specific timing of the post-merge hook

   The post-merge hook runs right after a merge finishes, allowing automation of follow-up tasks.

3. Final Answer:

   To run commands automatically after a merge completes -> Option D

4. Quick Check:

   post-merge hook = runs after merge [OK]

Hint: Post-merge hook runs after merge finishes [OK]

Common Mistakes:

• Confusing post-merge with pre-merge hooks
• Thinking it prevents merges
• Assuming it creates or deletes branches

2. Which of the following is the correct way to make a post-merge hook script executable on a Unix-like system?

easy

A. chmod 777 .git/hooks/post-merge

B. chmod +x .git/hooks/post-merge

C. git hook enable post-merge

D. chmod 644 .git/hooks/post-merge

Solution

1. Step 1: Understand file permissions for executable scripts

   To run a script as a hook, it must have executable permission, usually set with chmod +x.

2. Step 2: Identify the correct command

   chmod +x .git/hooks/post-merge sets the executable bit without giving excessive permissions.

3. Final Answer:

   chmod +x .git/hooks/post-merge -> Option B

4. Quick Check:

   Make hook executable = chmod +x [OK]

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

Common Mistakes:

• Using chmod 777 which is insecure
• Using chmod 644 which is not executable
• Trying git commands to enable hooks

3. Given this post-merge hook script saved in .git/hooks/post-merge and made executable:

#!/bin/sh
npm install
npm run build

What will happen after you run git merge feature-branch?

medium

A. The dependencies will install and the project will build automatically

B. The merge will fail because of the script

C. Nothing happens because post-merge hooks do not run automatically

D. Only npm install will run, not npm run build

Solution

1. Step 1: Understand what the post-merge hook script does

   The script runs npm install to install dependencies, then npm run build to build the project.

2. Step 2: Know when the post-merge hook runs

   It runs automatically after a successful merge, so both commands will execute in order.

3. Final Answer:

   The dependencies will install and the project will build automatically -> Option A

4. Quick Check:

   post-merge runs script after merge [OK]

Hint: Post-merge runs script commands after merge [OK]

Common Mistakes:

• Thinking hooks don't run automatically
• Assuming only first command runs
• Believing merge fails due to hook

4. You wrote a post-merge hook script but it does not run after merging. Which of these is the most likely cause?

medium

A. The script file is not executable

B. You forgot to commit the hook script

C. The merge was done with git rebase

D. The script is saved outside the .git/hooks directory

Solution

1. Step 1: Check script execution permissions

   If the script is not executable, Git will not run it after merge.

2. Step 2: Understand that hooks are local and not committed

   Hooks are not shared via commits, so forgetting to commit is irrelevant.

3. Step 3: Consider merge method and script location

   Rebase does not trigger post-merge, but the question states a merge was done. Also, hooks must be in .git/hooks.

4. Final Answer:

   The script file is not executable -> Option A

5. Quick Check:

   Non-executable script = hook won't run [OK]

Hint: Check if hook script has executable permission [OK]

Common Mistakes:

• Thinking hooks are shared via commits
• Confusing merge with rebase triggers
• Saving script outside .git/hooks folder

5. You want to ensure that after every merge, your Python project automatically installs new dependencies listed in requirements.txt and runs tests. Which post-merge hook script is the best choice?

hard

A. #!/bin/sh
git pull
pytest

B. #!/bin/sh
npm install
npm test

C. #!/bin/sh
pip install -r requirements.txt
pytest

D. #!/bin/sh
pip uninstall -r requirements.txt
pytest

Solution

1. Step 1: Identify the correct commands for Python dependency installation and testing

   pip install -r requirements.txt installs dependencies; pytest runs tests.

2. Step 2: Evaluate other options for relevance

   #!/bin/sh npm install npm test uses npm commands for JavaScript, not Python. #!/bin/sh pip uninstall -r requirements.txt pytest uninstalls dependencies which is wrong. #!/bin/sh git pull pytest pulls changes again, unnecessary after merge.

3. Final Answer:

   #!/bin/sh pip install -r requirements.txt pytest -> Option C

4. Quick Check:

   Python post-merge = pip install + pytest [OK]

Hint: Use pip install and pytest for Python post-merge tasks [OK]

Common Mistakes:

• Using npm commands for Python projects
• Uninstalling dependencies instead of installing
• Running git pull again after merge