The current implementation results in generated jobs performing a full 'infinity' checkout of the branches specified in the 'master' job.
It would be ideal if the SCM specification for the branches to generate jobs for and the SCM specification for checking out into the workspace were somehow separately controlled. In particular we don't want the generated jobs to perform a source checkout at all. Even just a checkbox to prevent the checkout in generated jobs would suffice.
This is useful for generated jobs for branches that either re-use a workspace on a node from another job or otherwise don't require a checkout or otherwise need to do the checkout differently.