Contributor Guide

Thank you for your interest in PiperCI.

Getting Started

Follow the deployment instructions for the PiperCI Installer for the

Read Working with PiperCI Functions for more info on PiperCI functions.

Git Workflow

Use trunk-based development when proposing contributions to this repository. Submit your proposed change as a merge request from a feature branch in your fork.

Commit Message Guidelines

Always write clear commit messages.

We have very precise rules, following the Conventional Commits standard, that govern how commit messages may be formatted. This leads to more readable messages that are easy to follow when looking through the project history. But also, we use the commit messages to generate the CHANGELOG based on angularjs-style commits.

These rules are enforced across our projects by our CI pipelines using this commitchecker job commitlint

Commit Message Format

Each commit message consists of a header, a body and a footer. The header has a special format that includes a type, a scope and a subject:

<type>(<scope>): <subject>

The header is mandatory and the scope of the header is optional.

Any line of the commit message cannot be longer 100 characters! This allows the message to be easier to read in the browser as well as in various git tools.


If the commit reverts a previous commit, it should begin with revert:, followed by the header of the reverted commit. In the body it should say: This reverts commit <hash>., where the hash is the SHA of the commit being reverted.


Must be one of the following:

  • build: changes that affect the build system or external dependencies

  • ci: changes to our CI configuration files and scripts

  • chore: Changes to the build process or auxiliary tools and libraries such as documentation generation

  • docs: Documentation only changes

  • feat: A new feature

  • fix: A bug fix

  • perf: A code change that improves performance

  • refactor: A code change that neither fixes a bug nor adds a feature

  • revert: Reverting a previously committed change

  • style: Changes that do not affect the meaning of the code (white-space, formatting, missing semi-colons, etc)

  • test: Adding missing or correcting existing tests


The scope could be anything specifying place of the commit change. For example $location, $browser, $compile, $rootScope, ngHref, ngClick, ngView, etc…

You can use * when the change affects more than a single scope.


The subject contains succinct description of the change:

  • use the imperative, present tense: “change” not “changed” nor “changes”

  • don’t capitalize first letter

  • no dot (.) at the end


Just as in the subject, use the imperative, present tense: “change” not “changed” nor “changes”. The body should include the motivation for the change and contrast this with previous behavior.


We use pytest as our test automation framework. Generally, add adequate unit tests under /tests/unit per merge request.

Ensure your tests pass before submitting a merge request in the repository.

To run all tests you should use tox: tox

Going forward, functional (i.e., end-to-end) testing will also be done using tox

Coding Style

Much of PiperCI is written in Python. For all Python code, we will adhere to PEP8 with a few exceptions. For such exceptions, see the python-project\tox.ini.example configuration file.

We use flake8 for basic linting checks.

Coding Standards

  • Code is to run in Python 3.7.3

  • New code should use type hinting for external interfaces intended to be used by other developers. See: PEP 484

  • Merge requests must pass the standard linting.

  • DRY principles unless it doesn’t make sense.

  • Pytest coverage must be greater then 80%

  • All code must be contained in a valid module with an

  • Modules should make use of exceptions, functions should not introduce side effects… like print() or sys.exit()

  • Logging and debug should use the python standard logging library