The idea is these should replace the current Shelve and Unshelve
dialogs. They will support shelving and unshelving, and also
checkpointing (saving a new version of a shelf) and restoring
(retrieving an old version of a shelf).
I plan to get these implemented on a TSVN branch next, that will be
built against Subversion's 'shelve-checkpoint' branch where the API and
command-line UI currently exists.