The mechanism to use parse-options API to automate the command line
completion continues to get extended and polished.

* nd/parseopt-completion-more:
  completion: use __gitcomp_builtin in _git_cherry
  completion: use __gitcomp_builtin in _git_ls_tree
  completion: delete option-only completion commands
  completion: add --option completion for most builtin commands
  completion: factor out _git_xxx calling code
  completion: mention the oldest version we need to support
  git.c: add hidden option --list-parseopt-builtins
  git.c: move cmd_struct declaration up