core.whitespace: cr-at-eol

core.whitespace: cr-at-eol

This new error mode allows a line to have a carriage return at the
end of the line when checking and fixing trailing whitespace errors.

Some people like to keep CRLF line ending recorded in the repository,
and still want to take advantage of the automated trailing whitespace
stripping.  We still show ^M in the diff output piped to "less" to
remind them that they do have the CR at the end, but these carriage
return characters at the end are no longer flagged as errors.

Signed-off-by: Junio C Hamano <gitster@pobox.com>