\def\ProvidesFile#1{% % test of writing
\begingroup % comments
\catcode`\ 10 % %
\ifnum \endlinechar<256 % %
\ifnum \endlinechar>\m@ne %
\catcode\endlinechar 10 % %
\fi
\fi
\@makeother\/%
\@ifnextchar[{\@providesfile{#1}}{\@providesfile{#1}[]}}