Branch will run a specific automation step.

CreateBranches goes to each repo and creates the branches.

CreateToolsImage update the BRANCH for the docker image name.

IstioReleaseBuilderUpdates updates master to use next release base image, and build dev images based on next release.

SetupProw goes to the test-infra repo and runs the commands to generate the config files for the new release.

StopPublishingLatest stops prow from publishing the `latest` artifacts, leaving only the release-dev artifacts.

UpdateCodeOwners goes to each repo and updates CODEOWNERS to just be the release managers.

UpdateCommonFiles goes to each repo and runs the command to update the common files.

UpdateCommonFilesCommon update the common-files repo for the new release.

UpdateDependencies runs commands in the istio/istio repo: ./bin/update_deps.sh and make gen.