Github pre commit hook to validate commit message and description

10 Jun 2024 | category: git | Comments
#git #devops

To set up a Git pre-commit hook to validate the length of commit messages and descriptions, you can create a script that will be executed before each commit. This script can be placed in the .git/hooks directory of your repository. Here’s how you can do it:

  1. Navigate to your repository:
cd /path/to/your/repo
  1. Create a pre-commit hook: Create a file named pre-commit in the .git/hooks directory:
touch .git/hooks/pre-commit
chmod +x .git/hooks/pre-commit
  1. Edit the pre-commit hook:

Open the .git/hooks/pre-commit file in your preferred text editor and add the following script:

#!/bin/sh

# Define the maximum lengths for the commit message subject and description
MAX_SUBJECT_LENGTH=50
MAX_DESCRIPTION_LENGTH=72

# Get the commit message
commit_msg_file=$(git rev-parse --git-dir)/COMMIT_EDITMSG
commit_msg=$(head -n1 $commit_msg_file)
commit_desc=$(tail -n +2 $commit_msg_file | grep -vE '^[[:space:]]*$')

# Check the length of the commit subject
if [ ${#commit_msg} -gt $MAX_SUBJECT_LENGTH ]; then
    echo "Error: The commit message subject is too long (maximum $MAX_SUBJECT_LENGTH characters)."
    echo "Subject: $commit_msg"
    exit 1
fi

# Check the length of each line in the commit description
while IFS= read -r line; do
    if [ ${#line} -gt $MAX_DESCRIPTION_LENGTH ]; then
        echo "Error: A line in the commit description is too long (maximum $MAX_DESCRIPTION_LENGTH characters)."
        echo "Line: $line"
        exit 1
    fi
done <<< "$commit_desc"

exit 0
  1. Make the script executable:

Ensure that the pre-commit file is executable:

chmod +x .git/hooks/pre-commit