commit-msg

Learn message validation with the commit-msg hook.

What Is the commit-msg Hook?

The commit-msg hook runs before Git creates the commit and is used to validate the commit message. Git passes the path of the commit message file to this hook as an argument. The script can read this file and check whether the message follows specific rules.

#!/bin/sh
message_file="$1"
cat "$message_file"

Validate the Commit Message Format

To enforce a specific commit message format, you can read the message file inside commit-msg. For example, you can require messages to start with feat:, fix:, or docs:. Return a nonzero exit code for an invalid message to block the commit.

#!/bin/sh
message=$(cat "$1")
case "$message" in
  feat:*|fix:*|docs:*) exit 0 ;;
  *) echo "Invalid message"; exit 1 ;;
esac

Exercise Validate a Commit Message Format

Write a Shell script for commit-msg. Read the message file from the first argument using cat. If the message starts with fix:, exit successfully; otherwise print Invalid commit message and use exit 1.

Show example solution

message=$(cat "$1")
case "$message" in
  fix:*) exit 0 ;;
  *) echo "Geçersiz commit mesajı"; exit 1 ;;
esac

Test yourself

What information does the commit-msg hook receive as an argument?
- The complete history of the current branch
- The path of the file containing the commit message
- The remote repository URL
- The file list of the latest commit
Show answer

The path of the file containing the commit message — Git passes the temporary commit message file path as the first argument to the commit-msg hook. The script can read this file.

Read the Commit Message File

#!/bin/sh
message=$(cat "____")

Show answer

#!/bin/sh
message=$(cat "$1")

commit-msg Components

commit-msg

Runs before message acceptance
$1

Path of the message file
cat

Reads the file contents
feat:

New feature message

Next lesson: Summary - Hooks

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