anchor.diff:      // run ``task`` and record the updated dependency stack in ``st``.
       | task :: tasks, [] ->
         debug "Loading" task;
  +      progress_callback task;
         Options.restore_cmd_line_options false |> ignore;
         let timestamped_task = update_task_timestamps task in
         let push_kind = if Options.lax () then LaxCheck else FullCheck in
  
positive.code: The original value of the ``repl_deps_stack`` field in ``st`` is used to skip
  already completed tasks.
  
  This function is stateful: it uses ``push_repl`` and ``pop_repl``. **)
  let run_repl_ld_transactions (st: repl_state) (tasks: list<repl_task>) =
    let debug verb task =
      if Options.debug_any () then
        Util.print2 "%s %s" verb (string_of_repl_task task) in
  
negative.code:    "describe-protocol"; "describe-repl"; "exit";
     "lookup"; "lookup/context"; "lookup/documentation"; "lookup/definition";
     "peek"; "pop"; "push"; "search"; "segment";
     "vfs-add"; "tactic-ranges"; "interrupt"; "progress"]
  
  exception InvalidQuery of string
  type query_status = | QueryOK | QueryNOK | QueryViolatesProtocol
  