Merge branch 'jk/argv-array-for-child-process'

* jk/argv-array-for-child-process:
  argv-array: drop "detach" code
  get_importer: use run-command's internal argv_array
  get_exporter: use argv_array
  get_helper: use run-command's internal argv_array
  git_connect: use argv_array
  run_column_filter: use argv_array
  run-command: store an optional argv_array