\documentclass{article}

\begin{document}

Lines which end with the ignore keyword are not indented or wrapped even if they are long % tex-fmt: skip

% tex-fmt: off
It is also possible to ignore blocks
  of lines together and not indent them
    even like this
% tex-fmt: on

  Not ignored

  % tex-fmt: on

  Not ignored

  % tex-fmt: off

  Ignored

  % tex-fmt: off

  Ignored

  % tex-fmt: on

  Not ignored

  % tex-fmt: off

  Ignored

\end{document}
