• Each feature/bug fix should be done on its own Git branch so they can be reviewed and merged independently. Refer to Using Git for how to do this. Please ask for help on Zulip if you have questions about using Git after reading that page.
• Commits should be as small as they can while still building. The smaller the commit, the easier it is to review. It also makes it easier to revert if it is later identified as the source of a bug. If you have lots of changes that you need to commit, a GUI Git client can be helpful for picking out specific changes for multiple small commits.
• Every commit should build. This is important so git bisect works.
• Commit messages should succinctly describe what is changed in that commit and why. For example, this is a good commit message:

DlgPrefEffects: add QListWidget to set order of chains

This order will soon be used by new ControlObjects to load them
from controllers.

The first line should be <= 50 characters and the body should line wrap at 72 characters. This is not a good commit message:

address comments from PR review

Refer to How to Write a Git Commit Message for more details.

• Generally, prefer merging to rebasing. Do not rebase unless you have discussed that with whoever is reviewing the pull request. When you rebase a branch with an open pull request, prior review comments made inline in the code on GitHub lose their connection to that spot in the code. If you want to correct minor mistakes with a rebase or git commit --amend within a few minutes of pushing commits, that is okay as long as no one has started reviewing those commits yet.
• If you are helping with someone else's pull request that is not yet merged, open a pull request targeted at their fork. Leave a comment on the upstream pull request (which targets mixxxdj/mixxx) with a link to your pull request so other Mixxx contributors are aware of your changes.
• Low risk bug fixes should be targeted at the stable branch (currently 2.2). However, bug fixes for the stable branches must have a direct impact on users. If you spot a minor bug reading the code or only want to clean up the code, target that at the master or beta branch.
• Controller mappings should be targeted at the stable branch unless they use features that are new in the beta or master branch.
• If you are making changes to the GUI with a pull request, please post before and after screenshots of the changes.
• Please help review other people's pull requests. When others review your pull requests, please return the favor. The continued progress of Mixxx depends on all of us working together. Even if you are not familiar with the area of the code being changed in a pull request, you can be helpful by building the branch, verifying that it works as described, and commenting with feedback about the user experience design.
• If you demonstrate good coding skills, help review pull requests, contribute major features, and show a commitment to Mixxx over time, we may invite you to the core team.

Mixxx core team members are contributors who have write access to the upstream mixxxdj repositories on GitHub, access to the Jenkins web interface for the build servers, and access to the private Zulip stream for the core team.

• Enable two-factor authentication (2FA) for your GitHub account.
• Never force push to an upstream repository (mixxxdj). If you encounter an error from Git saying you would need to force push, stop what you are doing and discuss the situation on Zulip.
• Only push directly to an upstream repository (mixxxdj) for trivial, uncontroversial changes like fixing a typo.
• All non-trivial contributions should be made with a pull request, just like any other contributor who does not have write access. Do not merge your own pull requests.
• You may merge someone else's pull request as the only reviewer if no other contributors have expressed concerns about the changes or said they want to review the code. Please do not merge pull requests immediately; allow at least a day or two for others to comment. Remember we are all volunteers and cannot respond to everything immediately.
• If there is disagreement about changes in a pull request, do not merge it until a consensus has been reached.
• Check CI to ensure builds work and tests pass before merging. If CI timed out, either manually restart it or build the branch and run the tests locally before merging.
• When you merge a pull request to a stable branch, merge the stable branch to the beta branch afterwards. If you merge a pull request to a beta branch, merge the beta branch to master afterwards. When backporting, cherry-pick or rebase rather than merge.
• Default to open; only post in the private Zulip stream for discussions that have a reason to be private. Most of the time, post to a public Zulip stream so anyone can participate in the discussion.
• When Mixxx participates in Google Summer of Code, you may volunteer as a mentor if you like.