grep --all-match

This lets you say:

	git grep --all-match -e A -e B -e C

to find lines that match A or B or C but limit the matches from
the files that have all of A, B and C.

This is different from

	git grep -e A --and -e B --and -e C

in that the latter looks for a single line that has all of these
at the same time.

Signed-off-by: Junio C Hamano <junkio@cox.net>

builtin-grep.c

@@ -596,6 +596,10 @@ int cmd_grep(int argc, const char **argv, const char *prefix)
 					    GREP_CLOSE_PAREN);
 			continue;
 		}
+		if (!strcmp("--all-match", arg)) {
+			opt.all_match = 1;
+			continue;
+		}
 		if (!strcmp("-e", arg)) {
 			if (1 < argc) {
 				append_grep_pattern(&opt, argv[1],