grep -P: Fix matching ^ and $

When "git grep" is run with -P/--perl-regexp, it doesn't match ^ and $ at the beginning/end of the line. This is because PCRE normally matches ^ and $ at the beginning/end of the whole text, not for each line, and "git grep" passes a large chunk of text (possibly containing many lines) to pcre_exec() and then splits the text into lines. This makes "git grep -P" behave differently from "git grep -E" and also from "grep -P" and "pcregrep": $ cat file a b $ git grep --no-index -P '^ ' file $ git grep --no-index -E '^ ' file file: b $ grep -c -P '^ ' file b $ pcregrep -c '^ ' file b Reported-by: Zbigniew Jędrzejewski-Szmek <zbyszek@in.waw.pl> Signed-off-by: Michał Kiedrowicz <michal.kiedrowicz@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>