clone,fetch: catch non positive --depth option value

Instead of simply ignoring the value passed to --depth option when
it is zero or negative, catch and report it as an error to let
people know that they were using the option incorrectly.

Original-patch-by: Andrés G. Aragoneses <knocte@gmail.com>
Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/builtin/fetch.c b/builtin/fetch.c
index 5647055..72930fc 100644
--- a/builtin/fetch.c
+++ b/builtin/fetch.c
@@ -1045,6 +1045,10 @@
 		}
 	}
 
+	/* no need to be strict, transport_set_option() will validate it again */
+	if (depth && atoi(depth) < 1)
+		die(_("depth %s is not a positive number"), depth);
+
 	if (recurse_submodules != RECURSE_SUBMODULES_OFF) {
 		if (recurse_submodules_default) {
 			int arg = parse_fetch_recurse_submodules_arg("--recurse-submodules-default", recurse_submodules_default);