Release checklist

Run build-scripts/create-release.py -R libsdl-org/SDL --ref <branch> to do a dry run creating the release assets. Verify that the archives are correct.
Tag the release, e.g. git tag release-3.8.0; git push --tags
Run build-scripts/create-release.py -R libsdl-org/SDL --ref <release-tag> to have GitHub Actions create release assets. This makes sure the revision string baked into the archives is correct.
Verify that the source archive REVISION.txt has the correct release tag.
Sign the source archives and upload everything to libsdl.org
Create a GitHub release and attach the archives you just generated.

New feature release

Update WhatsNew.txt
Bump version number to 3.EVEN.0:
- ./build-scripts/update-version.sh 3 EVEN 0
Do the release
Immediately create a branch for patch releases, e.g. git branch release-3.EVEN.x
Bump version number from 3.EVEN.0 to 3.(EVEN+1).0
- ./build-scripts/update-version.sh 3 EVEN+1 0
Update the website file include/header.inc.php to reflect the new version

Bump version number from 3.Y.Z to 3.Y.(Z+1) (Y is even)
- ./build-scripts/update-version.sh 3 Y Z+1
Do the release
Update the website file include/header.inc.php to reflect the new version

Bump version number from 3.Y.Z to 3.Y.(Z+1) (Y is odd)
- ./build-scripts/update-version.sh 3 Y Z+1
Do the release