docs: def cmd_switch_workdir(new_workdir):
      """
      Arguments: <new work directory path>
  
      Change current Paperwork's work directory.
  
      Does *not* update the index.
      You should run 'paperwork-shell rescan' after this command.
  
      Possible JSON replies:
          --
          {
              "status": "error", "exception": "yyy",
              "reason": "xxxx", "args": "(xxxx, )"
          }
          --
          {
              "status": "ok",
              "old_workdir": "file:///home/jflesch/papers",
              "new_workdir": "file:///tmp/papers",
          }
      """
      new_workdir = FS.safe(new_workdir)
      if not FS.exists(new_workdir) or not FS.isdir(new_workdir):
          sys.stderr.write("New work directory {} doesn't exists".format(
              new_workdir
          ))
          return
      pconfig = config.PaperworkConfig()
      pconfig.read()
      r = {
          'old_workdir': pconfig.settings['workdir'].value,
          'new_workdir': new_workdir
      }
      pconfig.settings['workdir'].value = new_workdir
      pconfig.write()
      reply(r)