Versioning

Pillow follows Semantic Versioning. From https://semver.org/:

Given a version number MAJOR.MINOR.PATCH, increment the:

MAJOR version when you make incompatible API changes,

MINOR version when you add functionality in a backwards compatible manner, and

PATCH version when you make backwards compatible bug fixes.

Quarterly releases (referred to as "Main Release" in the checklist below) bump at least the MINOR version, as new functionality has likely been added in the prior three months.

A quarterly release bumps the MAJOR version when make incompatible API changes are made, such as removing deprecated APIs or dropping an EOL Python version. In practice, these occur every 12-18 months, guided by Python's EOL schedule, and any APIs that have been deprecated for at least a year are removed at the same time.

PATCH versions ("Point Release" or "Embargoed Release" in the checklist below) are for security, installation or critical bug fixes. These are less common as it is preferred to stick to quarterly releases.

Between quarterly releases, ".dev0" is appended to the version, indicating that this is not a formally released copy.

Release Checklist

Main Release

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

Open a release ticket e.g. https://github.com/python-pillow/Pillow/issues/3154
Develop and prepare release in master branch.
Check GitHub Actions and AppVeyor to confirm passing tests in master branch.
Check that all of the wheel builds Pillow Wheel Builder pass the tests in Travis CI and GitHub Actions.
In compliance with PEP 440, update version identifier in src/PIL/_version.py
Update CHANGES.rst.
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 --all
git push --tags

Create source distributions e.g.:
```
make sdist
```
Create binary distributions
Upload all binaries and source distributions e.g. twine upload dist/Pillow-5.2.0*
Publish the release on GitHub
In compliance with PEP 440, increment and append .dev0 to version identifier in src/PIL/_version.py

Point Release

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

Make necessary changes in master branch.
Update CHANGES.rst.
Check out release branch e.g.:
```
git checkout -t remotes/origin/5.2.x
```
Cherry pick individual commits from master 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
git push --tags
```
Create source distributions e.g.:
```
make sdist
```
Create binary distributions
Upload all binaries and source distributions e.g. twine upload dist/Pillow-5.2.1*
Publish the release on GitHub

Embargoed Release

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 master, 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 2.5.x
git push origin --tags

Create source distributions e.g.:
```
make sdist
```
Create binary distributions
Publish the release on GitHub

Binary Distributions

Windows

Contact @cgohlke for Windows binaries via release ticket e.g. https://github.com/python-pillow/Pillow/issues/1174.
Download and extract tarball from @cgohlke and twine upload *.

Mac and Linux

Use the Pillow Wheel Builder:

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

Download wheels from the Pillow Wheel Builder release.

Publicize Release

Announce release availability via Twitter e.g. https://twitter.com/PythonPillow/status/1013789184354603010

Documentation

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

Docker Images

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]]

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