Since tags and branches are handled by git and not metacello, with Baseline you need just single method BaselineOfX>>baseline:

see for example��https://github.com/dalehenrich/filetree/blob/gemstone2.4/repository/BaselineOfFileTree.package/BaselineOfFileTree.class/instance/baseline..st or��https://github.com/dynacase/dynacase/blob/master/repository/BaselineOfDynaCASE.package/BaselineOfDynaCASE.class/instance/baseline..st

But of course this may not apply for your specific use case.

Peter