Merge branch 'bk/refs-multi-update'

Give "update-refs" a "--stdin" option to read multiple update requests and perform them in an all-or-none fashion. * bk/refs-multi-update: update-ref: add test cases covering --stdin signature update-ref: support multiple simultaneous updates refs: add update_refs for multiple simultaneous updates refs: add function to repack without multiple refs refs: factor delete_ref loose ref step into a helper refs: factor update_ref steps into helpers refs: report ref type from lock_any_ref_for_update reset: rename update_refs to reset_refs