How to use the command 'gitlint' (with examples)
Gitlint is a command-line utility designed to ensure that your commit messages adhere to a certain style as per the guidelines you define. Whether working in a collaborative environment or maintaining clean project history for future reference, consistent commit message styles are crucial. Gitlint helps automate this by checking your commit messages for style violations and can be customized with user-defined rules.
Use case 1: Check the last commit message
Code:
gitlint
Motivation: Checking the last commit message is a quick way to ensure that your recent contributions adhere to the project’s commit message guidelines. This step is especially useful just before you push your changes to ensure that the commit is well-formatted and thus, maintainable.
Explanation: By simply running gitlint without any additional arguments, gitlint defaults to checking the most recent commit message in your current branch. This is typically the commit you just made, making it an efficient check to perform.
Example Output:
1: T3 B6 Commit message body line too long (88>72): "This commit message is too long and exceeds the recommended line length for readability."
Use case 2: The range of commits to lint
Code:
gitlint --commits single_refspec_argument
Motivation: Sometimes, projects demand a linting check across multiple commits, especially during the integration of a feature branch. This is crucial when dealing with a series of related changes, ensuring that the entire set adheres to commit message guidelines for clarity and consistency.
Explanation: The --commits argument allows you to specify a range of commits to be checked. You can use a refspec to define the range, for example, HEAD~3..HEAD to check the last three commits. This flexibility is vital for reviewing batch changes.
Example Output:
Commit ca82a6: Missing sign-off trailer
3: B4 Second line is not empty: "More fixes for the issue."
Use case 3: Path to a directory or Python module with extra user-defined rules
Code:
gitlint --extra-path path/to/directory
Motivation: Different projects might have different standards. To support this, gitlint allows you to implement custom rules. This is crucial for teams with unique conventions that are not covered by built-in linting rules.
Explanation: By using the --extra-path argument, you specify a directory containing Python files that define extra linting rules. This allows significant flexibility by adapting gitlint to your specific requirements and is particularly useful for adhering to various internal team guidelines.
Example Output:
CustomRule1: This commit does not meet our internal standard.
Use case 4: Start a specific CI job
Code:
gitlint --target path/to/target_directory
Motivation: In continuous integration (CI) environments, automating style checks is essential. Using gitlint as part of the CI pipeline ensures all commit messages are checked before integration, maintaining project history hygiene.
Explanation: The --target argument specifies the target directory of the repository inside your CI job. This is important when your CI setup involves multiple repositories or paths, ensuring gitlint checks are executed in the correct context.
Example Output:
CI job started: Commit message checks running.
Use case 5: Path to a file containing a commit-msg
Code:
gitlint --msg-filename path/to/filename
Motivation: Often, you may want to check a commit message stored in a specific file, which is typical during scripting or when working with offline commit drafts. This ensures pre-validation before the message is committed.
Explanation: The --msg-filename argument lets you point gitlint to a specific file containing a commit message rather than targeting the current HEAD commit. This enables custom workflows, such as validating prepared commit messages before applying them.
Example Output:
File check: The commit message is compliant.
Use case 6: Read staged commit meta-info from the local repository
Code:
gitlint --staged
Motivation: Enabling checks on the staged commit data can catch issues before they are officially committed. This is particularly useful in pre-commit hook scripts that automatically validate message compliance.
Explanation: Using the --staged argument instructs gitlint to assess the commit message that has been staged in the local repository, instead of the already committed ones. This preemptive checking helps prevent errors earlier in the workflow.
Example Output:
Staged commit check: Errors found, please review your commit message.
Conclusion:
Gitlint provides a crucial service for developers by maintaining the integrity and readability of commit messages. With its flexibility to check specific commits, include custom rules, and integrate into CI pipelines, gitlint is a highly configurable tool that supports a wide range of workflows, ensuring project history remains organized and clear. Whether you are managing a large open-source project or a small team of developers, gitlint is an essential addition to your development toolkit.
