rev-parse: introduce --is-bare-repository

Signed-off-by: Matthias Lederhofer <matled@gmx.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/builtin-rev-parse.c b/builtin-rev-parse.c
index 37addb2..71d5162 100644
--- a/builtin-rev-parse.c
+++ b/builtin-rev-parse.c
@@ -352,6 +352,11 @@
 						: "false");
 				continue;
 			}
+			if (!strcmp(arg, "--is-bare-repository")) {
+				printf("%s\n", is_bare_repository() ? "true"
+						: "false");
+				continue;
+			}
 			if (!prefixcmp(arg, "--since=")) {
 				show_datestring("--max-age=", arg+8);
 				continue;