commit-msg hook for message validation in Git - Mini Project: Build & Apply

commit-msg hook for message validation

📖 Scenario: You are working on a team project where every commit message must start with a ticket number like PROJ-123 followed by a short description. This helps everyone understand what the commit is about and links it to the right task.

🎯 Goal: Create a commit-msg Git hook script that checks if the commit message starts with a ticket number pattern PROJ- followed by digits. If the message does not match, the commit should be rejected with a clear error message.

📋 What You'll Learn

Create a commit-msg hook script file

Check the commit message file content for the pattern PROJ- followed by digits at the start

Reject the commit if the pattern is missing with a message

Allow the commit if the pattern is present

💡 Why This Matters

🌍 Real World

Teams use commit-msg hooks to enforce commit message standards, improving project tracking and collaboration.

💼 Career

Knowing how to write Git hooks is useful for DevOps roles and software developers to maintain code quality and workflow consistency.

1

Create the commit-msg hook script file

Create a file named commit-msg inside the .git/hooks/ directory with the first line #!/bin/sh to specify the shell interpreter.

Git

# Create the commit-msg hook file with the shebang line
# Your code here

Need a hint?

The first line of a shell script should be #!/bin/sh to tell Git which shell to use.

2

Read the commit message from the file

Add a line to read the commit message from the file path passed as the first argument $1 into a variable named commit_msg.

Git

#!/bin/sh
# Read the commit message from the file
# Your code here

Need a hint?

Use commit_msg=$(cat "$1") to read the commit message content.

3

Check if commit message starts with 'PROJ-' followed by digits

Add an if statement that uses grep -qE to check if commit_msg starts with the pattern PROJ- followed by one or more digits. If it does not match, print Error: Commit message must start with PROJ- followed by ticket number. and exit with status 1.

Git

#!/bin/sh
commit_msg=$(cat "$1")
# Check commit message pattern
# Your code here

Need a hint?

Use grep -qE '^PROJ-[0-9]+' to check the pattern at the start of the message.

4

Allow commit if message is valid

Add a line to exit with status 0 at the end of the script to allow the commit if the message passed the check.

Git

#!/bin/sh
commit_msg=$(cat "$1")
if ! echo "$commit_msg" | grep -qE '^PROJ-[0-9]+'; then
  echo "Error: Commit message must start with PROJ- followed by ticket number."
  exit 1
fi
# Allow commit
# Your code here

Need a hint?

Use exit 0 to indicate success and allow the commit.