let concat ~(run_with : Machine.t) bunch_of_files ~result_path =
    let open KEDSL in
    let program =
      Program.(
        exec ["mkdir"; "-p"; Filename.dirname result_path]
        && shf "cat %s > %s"
          (List.map bunch_of_files
             ~f:(fun o -> Filename.quote o#product#path)
           |> String.concat ~sep:" ") result_path
      ) in
    let name =
      sprintf "concat-all-%s" (Filename.basename result_path) in
    workflow_node
      (single_file result_path ~host:Machine.(as_host run_with))
      ~name
      ~edges:(
        on_failure_activate Remove.(file ~run_with result_path)
        :: List.map ~f:depends_on bunch_of_files)
      ~make:(Machine.run_stream_processor run_with ~name  program)