Merge branch 'jk/nested-points-at'

"git tag --list --points-at X" showed tags that directly refers to object X, but did not list a tag that points at such a tag, which has been corrected. * jk/nested-points-at: ref-filter: simplify return type of match_points_at ref-filter: avoid parsing non-tags in match_points_at() ref-filter: avoid parsing tagged objects in match_points_at() ref-filter: handle nested tags in --points-at option