Release Checklist

See https://pillow.readthedocs.io/en/stable/releasenotes/versioning.html for information about how the version numbers line up with releases.

Main Release

Released quarterly on January 2nd, April 1st, July 1st and October 15th.

Open a release ticket e.g. #3154
Develop and prepare release in main branch.
Check GitHub Actions and AppVeyor to confirm passing tests in main branch.
Check that all the wheel builds pass the tests in the GitHub Actions "Wheels" workflow jobs by manually triggering them.
In compliance with PEP 440, update version identifier in src/PIL/_version.py
Run pre-release check via make release-test in a freshly cloned repo.

Create branch and tag for release e.g.:

git branch 5.2.x
git tag 5.2.0
git push --tags

Check the GitHub Actions "Wheels" workflow has passed, including the "Upload release to PyPI" job. This will have been triggered by the new tag.
Publish the release on GitHub.
In compliance with PEP 440, increment and append .dev0 to version identifier in src/PIL/_version.py and then:
```
git push --all
```

Released as needed for security, installation or critical bug fixes.

Make necessary changes in main branch.
Check out release branch e.g.:
```
git checkout -t remotes/origin/5.2.x
```
Cherry pick individual commits from main branch to release branch e.g. 5.2.x, then git push.
Check GitHub Actions and AppVeyor to confirm passing tests in release branch e.g. 5.2.x.
In compliance with PEP 440, update version identifier in src/PIL/_version.py
Run pre-release check via make release-test.
Create tag for release e.g.:
```
git tag 5.2.1
git push --tags
```
Create and check source distribution:
```
make sdist
```
Check the GitHub Actions "Wheels" workflow has passed, including the "Upload release to PyPI" job. This will have been triggered by the new tag.
Publish the release on GitHub and then:
```
git push
```

Released as needed privately to individual vendors for critical security-related bug fixes.

Prepare patch for all versions that will get a fix. Test against local installations.
Commit against main, cherry pick to affected release branches.
Run local test matrix on each release & Python version.
Privately send to distros.
Run pre-release check via make release-test
Amend any commits with the CVE #

On release date, tag and push to GitHub.

git checkout 2.5.x
git tag 2.5.3
git push origin --tags

Check the GitHub Actions "Wheels" workflow has passed, including the "Upload release to PyPI" job. This will have been triggered by the new tag.
Publish the release on GitHub and then:
```
git push origin 2.5.x
```

Announce release availability via Mastodon e.g. https://fosstodon.org/@pillow/110639450470725321

Make sure the default version for Read the Docs is up-to-date with the release changes

Update Pillow in the Docker Images repository

git clone https://github.com/python-pillow/docker-images
cd docker-images
./update-pillow-tag.sh [[release tag]]