# Source Code Management

# Branching Model

The PX4 project uses a three-branch Git branching model:

We try to retain a linear history through rebases (opens new window) and avoid the Github flow (opens new window). However, due to the global team and fast moving development we might resort to merges at times.

To contribute new functionality, sign up for Github (opens new window), then fork (opens new window) the repository, create a new branch (opens new window), add your changes, and finally send a pull request (opens new window). Changes will be merged when they pass our continuous integration (opens new window) tests.

All code contributions have to be under the permissive BSD 3-clause license (opens new window) and all code must not impose any further constraints on the use.

# Code Style Formatting

PX4 uses astyle (opens new window) for code formatting. Valid versions are

Once installed, formatting can be checked with ./Tools/astyle/check_code_style_all.sh. The output should be Format checks passed on a clean master. If that worked, make format can be used in the future to check and format all files automatically.

# In-Source Documentation

PX4 developers are encouraged to create appropriate in-source documentation.

Note

Source-code documentation standards are not enforced, and the code is currently inconsistently documented. We'd like to do better!

Currently we have two types of source-based documentation:

  • We encourage other in-source documentation where it adds value/is not redundant.

    TIP

    Developers should name C++ entities (classes, functions, variables etc.) such that their purpose can be inferred - reducing the need for explicit documentation.

# Commits and Commit Messages

Please use descriptive, multi-paragraph commit messages for all non-trivial changes. Structure them well so they make sense in the one-line summary but also provide full detail.

Component: Explain the change in one sentence. Fixes #1234
Prepend the software component to the start of the summary
line, either by the module name or a description of it.
(e.g. "mc_att_ctrl" or "multicopter attitude controller").
If the issue number is appended as <Fixes #1234>, Github
will automatically close the issue when the commit is
merged to the master branch.
The body of the message can contain several paragraphs.
Describe in detail what you changed. Link issues and flight
logs either related to this fix or to the testing results
of this commit.
Describe the change and why you changed it, avoid to
paraphrase the code change (Good: "Adds an additional
safety check for vehicles with low quality GPS reception".
Bad: "Add gps_reception_check() function").
Reported-by: Name <email@px4.io>

Use git commit -s to sign off on all of your commits. This will add signed-off-by: with your name and email as the last line.

This commit guide is based on best practices for the Linux Kernel and other projects maintained (opens new window) by Linus Torvalds.