grep: do not diagnose misspelt revs with --no-index

If we are using --no-index, then our arguments cannot be
revs in the first place. Not only is it pointless to
diagnose them, but if we are not in a repository, we should
not be trying to resolve any names.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Author: peff

builtin/grep.c

@@ -1201,7 +1201,7 @@ int cmd_grep(int argc, const char **argv, const char *prefix)
 	if (!seen_dashdash) {
 		int j;
 		for (j = i; j < argc; j++)
-			verify_filename(prefix, argv[j], j == i);
+			verify_filename(prefix, argv[j], j == i && use_index);
 	}
 
 	parse_pathspec(&pathspec, 0,

t/t7810-grep.sh

@@ -1043,6 +1043,11 @@ test_expect_success 'grep --no-index prefers paths to revs' '
 	test_cmp expect actual
 '
 
+test_expect_success 'grep --no-index does not "diagnose" revs' '
+	test_must_fail git grep --no-index o :1:hello.c 2>err &&
+	test_i18ngrep ! -i "did you mean" err
+'
+
 cat >expected <<EOF
 hello.c:int main(int argc, const char **argv)
 hello.c:	printf("Hello world.\n");