Code cleanup.

* jk/unused-params-even-more:
  parse_opt_ref_sorting: always use with NONEG flag
  pretty: drop unused strbuf from parse_padding_placeholder()
  pretty: drop unused "type" parameter in needs_rfc2047_encoding()
  parse-options: drop unused ctx parameter from show_gitcomp()
  fetch_pack(): drop unused parameters
  report_path_error(): drop unused prefix parameter
  unpack-trees: drop unused error_type parameters
  unpack-trees: drop name_entry from traverse_by_cache_tree()
  test-date: drop unused "now" parameter from parse_dates()
  update-index: drop unused prefix_length parameter from do_reupdate()
  log: drop unused "len" from show_tagger()
  log: drop unused rev_info from early output
  revision: drop some unused "revs" parameters