doobie uses sbt-ci-release which means all merges to master are pushed to Sonatype as snapshots and there's nothing to do.
To make a release, make sure you're on the right commit, then tag it using the format here. This will trigger a release build.
git tag -a v1.2.3 -m v1.2.3
git push --tagsTo update the doc site, check out the tag first.
git checkout v1.2.3
sbt docs/publishMicrosite