# Source code

* We use `git` for version control:
    * <{{ config.repo_url }}>
    * <{{ extra.mirror_url }}> (mirror)
* Our development branch is called `master`
* Prefix feature branch names with the issue ID (e.g. `4632_shift_fx`)
* Rebase with `-i --autosquash` before merging to preserve linear history
* Use non-fast forward (`--no-ff`) merges to track commit origin

## Contributing

We require an issue (or pull request) and [code review](#code-review) for any code contribution, except for the following, which can be committed directly to the `master` branch:

* Translations
* Documentation
* Infrastructure (`.github`)

The commit message for the first patch in the series should begin with the following header:

```
Ticket #<github_issue_number>: brief summary of the changes
```

### Signing off commits

!!! note
    DCO sign-off is different to "commit signing" using something like PGP or `gitsign`!

All contributors must acknowledge that they own the rights to the code they contribute by signing their commits with `git commit --amend -s` (adding a `Signed-off-by:` line to the commit message). This signifies that they abide by the [Developer Certificate of Origin, Version 1.1](https://developercertificate.org), which is also used by the Linux kernel.

### Branch lifecycle

!!! tip
    Don't forget to update the changelog as tracked on the current `NEWS-4.8.XX` wiki page!

1. Without PR
    - [ ] Assign issue to yourself
    - [ ] Update milestone
    - [ ] Link a branch
    - [ ] When ready for review:
         1. Add the label `state: in review`
         2. `@mention` the reviewers
    - [ ] Address comments with `git commit --fixup`
    - [ ] When approved, add a `state: approved` label
    - [ ] Make sure that CI is green and `git rebase -i --autosquash`
    - [ ] Proceed with the merge 
    - [ ] Manually delete the feature branch :material-alert-outline:
2. With PR
    - [ ] Open in draft mode if not ready yet
    - [ ] Switch to normal when ready for review
    - [ ] Update milestone
    - [ ] Invite reviewers
    - [ ] Address comments with `git commit --fixup`
    - [ ] Secure approvals
    - [ ] Make sure that CI is green and `/rebase`
    - [ ] Proceed with the merge 
    - [ ] Feature branch is deleted automatically

### Code review

!!! tip
    To substantially increase the likelihood that your changes will be accepted, be sure to add **tests** for the code you touch.

Contributions should be reviewed according to the following criteria:

*Motivation*
:   It should be clear what the purpose of the proposed changes is.

*Tests*
:   Changes should be accompanied by tests that document that the desired goals have been achieved.

*Code quality* (see [Coding style](coding-style.md))
:   
    * Code is split into logically independent commits
    * Changes are consistent with the rest of the code base
    * No large whitespace changes intermixed with logic changes

*Technical evaluation*
:   The code is a valid approach to the problem.

!!! note
    A lot of great (and sometimes not so great) literature has been written about code review over the decades. We don't intend to cover code review in detail here, just highlight the points that are most relevant to our process.

    A good place to start learning about code review in general is [Your code sucks, and I hate you](https://jml.io/your-code-sucks-and-i-hate-you/) by Jonathan Lange.

## Cleanup branch

For every release, we create a cleanup branch like `4633_cleanup` to aggregate small code changes, connected to the corresponding release ticket (e.g. [#4633]({{ config.repo_url }}issues/4633)).

* The cleanup branch should be created as needed and merged back in periodically (currently about once a month).
* Delete the cleanup branch after merging it into the main branch, and re-create it later with the same name if necessary.
* The cleanup branch should be merged into the main branch no later than a few weeks before the release, to allow enough time for the changes to be tested by developers and users.

Sometimes your patches might end up there. Don't worry, everything will be fine.