Merge branch 'kn/maintenance-is-needed'

"git maintenance" command learned "is-needed" subcommand to tell if it is necessary to perform various maintenance tasks. * kn/maintenance-is-needed: maintenance: add 'is-needed' subcommand maintenance: add checking logic in `pack_refs_condition()` refs: add a `optimize_required` field to `struct ref_storage_be` reftable/stack: add function to check if optimization is required reftable/stack: return stack segments directly