Search patterns in a file specified with -f can contain NUL characters.
The current code ignores all characters on a line after a NUL.
Pass the actual length of the line all the way from the pattern file to
fixmatch() and use it for case-sensitive fixed string matching.
Signed-off-by: Rene Scharfe <rene.scharfe@lsrfire.ath.cx>
Signed-off-by: Junio C Hamano <gitster@pobox.com>