The backend/backend/prepare-commit-msg hook in Git is a script that runs before the commit message editor is launched but after the default message is generated. Here are some detailed points about this hook:
- Purpose: This hook allows developers to edit the commit message template before the user starts typing. It can be used to add predefined information, format the message according to company standards, or even to enforce certain rules or checks before a commit can proceed.
- Invocation: The hook is invoked with three parameters:
- The name of the file that contains the commit log message.
- The source of the commit message, which can be 'message' (if a -m or -F option was given), 'template' (if a -t option was given or the configuration option commit.template is set in git config), 'merge' (if the commit is a merge or a .git/MERGE_MSG file exists), 'squash' (if the commit is a squash), or 'commit' (if none of the above).
- The commit SHA-1 (if applicable, for example, during a merge).
- Usage Examples:
- Automatically adding ticket numbers or JIRA issue keys to the commit message.
- Enforcing a specific commit message format or style (e.g., Conventional Commits).
- Adding custom headers or footers to commit messages.
- Performing checks like ensuring the commit message does not exceed a certain length or includes required sections.
- History and Context: Git hooks were introduced to allow developers to customize Git's behavior at various stages of the commit process. The prepare-commit-msg hook, in particular, was designed to help with commit message standardization, especially in large teams or projects where consistent commit messages are beneficial for tracking changes or integrating with other systems.
- Implementation:
- This hook must be executable. On Unix systems, you can make it executable by running
chmod +x .git/hooks/prepare-commit-msg.
- The hook script should modify the commit message file directly, as Git will use whatever is in the file after the hook completes.
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