Dimensions.yaml should be locked in and read-only as soon as the schema is created during the makeRepo phase. At the moment there is nothing stopping a repository from breaking if dimensions.yaml is updated in daf_butler and there is nothing stopping a user editing the config file after repository creation and breaking things.

We propose to remove dimensions.yaml from ButlerConfig and have it as an explicit argument for makeRepo (defaulting to pkg://lsst.daf.butler/configs/dimensions.yaml) which will then ensure that the dimensions configuration is locked in for that repository.

We will still require that it be possible to migrate a registry to a new dimensions definition but that migration should be by explicit request.