Merge branch 'kn/ref-filter-atom-parsing'

Merge branch 'kn/ref-filter-atom-parsing'

The ref-filter's format-parsing code has been refactored, in
preparation for "branch --format" and friends.

* kn/ref-filter-atom-parsing:
  ref-filter: introduce objectname_atom_parser()
  ref-filter: introduce contents_atom_parser()
  ref-filter: introduce remote_ref_atom_parser()
  ref-filter: align: introduce long-form syntax
  ref-filter: introduce align_atom_parser()
  ref-filter: introduce parse_align_position()
  ref-filter: introduce color_atom_parser()
  ref-filter: introduce parsing functions for each valid atom
  ref-filter: introduce struct used_atom
  ref-filter: bump 'used_atom' and related code to the top
  ref-filter: use string_list_split over strbuf_split