Pointless for GitSCM.getBranches() to be @Exported unless BranchSpec is an @ExportedBean!
[FIXED JENKINS-9843] PreBuildMergeOptions.getMergeRemote() cannot be @Exported, since the return type is not @ExportedBean.
Corrects attempted fix b3ddce6.
[JENKINS-9843] Forgot to record what problem this was fixing.