Merge branch 'nd/transport-positive-depth-only'

"git fetch --depth=0" was a no-op, and was silently
ignored. Diagnose it as an error.

* nd/transport-positive-depth-only:
  clone,fetch: catch non positive --depth option value

builtin/clone.c

@@ -796,6 +796,10 @@ int cmd_clone(int argc, const char **argv, const char *prefix)
 	if (option_local > 0 && !is_local)
 		warning(_("--local is ignored"));
 
+	/* no need to be strict, transport_set_option() will validate it again */
+	if (option_depth && atoi(option_depth) < 1)
+		die(_("depth %s is not a positive number"), option_depth);
+
 	if (argc == 2)
 		dir = xstrdup(argv[1]);
 	else