move parse_opt_points_at
add ref-filter api
tag: convert to ref-filter
ref-filter: implement --merged
tag: wire in ref-filter --merged
ref-filter: local/remote type matching
ref-filter: optionally resolve symrefs
branch: bump up get_head_description
branch: factor out default kinds
branch: roll show_detached HEAD into regular ref_list
branch: convert to ref-filter
ref-filter: learn about path-matching

This kind of breaks tag/branch matching, and should probably
be an option to ref-filter.
ref-filter: add util field
for-each-ref: update refinfo field names

To match upcoming ref-filter.
hook for-each-ref to ref-filter