Merge branch 'jc/refs-symref-referent'

The refs API has been taught to give symref target information to the users of ref iterators, allowing for-each-ref and friends to avoid an extra ref_resolve_* API call per a symbolic ref. * jc/refs-symref-referent: ref-filter: populate symref from iterator refs: add referent to each_ref_fn refs: keep track of unresolved reference value in iterators