PRLint: A linter for Pull Requests

PRLint helps improve the quality of git commits entering a repository's history by flagging commits that do not meet required standards.

For each Pull Request received, it lints the Pull Request's commits against a set of rules. Pull Requests that contain commits that do not meet the required standards will be set to RED and fail.

Tests the whole branch, not just git HEAD

The majority of testing services test only the final HEAD commit of a Pull Request. This is good enough when a team only cares about the final patch about to be applied, or in situations where the commits in every successful Pull Request are squashed into a single commit. However, some teams maintain git history and there are some conditions where the team may care about every commit in a Pull Request.

PRLint checks every commit in the Pull Request, to ensure that every one meets the requirements of the repository.

Fixup commits

Take, for example, fixup! commits created with git commit --fixup=. In Pull Request #1 there is a !fixup commit waiting to be squashed - it is highlighted here in red:

Although the diff of the Pull Request is valid, we want to block the merge of the Pull Request until the fixup commit is autosquashed. Otherwise the fixup commit will enter our master branch and pollute the history.

PRLint tests every commit in a Pull Request and fails if any commit doesn't pass the rules set for the repository.

TODO: Add failing status image and resolution.

Summary of default rules

TODO: will happen 😄

Further info

PRLint was originally called "nofixup" because it was built to catch fixup commits and set the HEAD commit of the Pull Request to failing if any were found.

You can read more about fixup commits and autosquashing in this thoughtbot article.

Values

• Open and accessible always: The project is open-source, you can take it and run your own instance.
• Generic and flexible: Although PRLint is written in Python, it can be used with any repository written in any languages. It aims to support as many workflows as possible.
• Multiple integrations: Primarily PRLint integrates with GitHub and works with the GitHub style of Pull Request. PRLint will integrate with as many services as possible.

Install

You will need python3, virtualenv and pip installed to be able to use this project in its current state. You'll also need GNU make or similar to be able to follow these install and testing instructions.

Clone this repository:

$ git clone git@github.com:jamescooke/prlint.git

Create a virtualenv containing Python3:

$ make venv

Activate and install requirements:

$ . venv/bin/activate
$ make install

Testing

With the virtual environment active, add the testing requirements:

$ make install-test

Run tests with pytest:

$ pytest prlint

Check linting with flake8 and isort, etc:

$ make -C prlint/ lint