From: Christian Kastner <ckk@kvr.at>
Date: Fri, 15 Jan 2016 22:15:30 +0100
Subject: crontab without arguments reads from stdin

If crontab is run without argument, then POSIX mandates that it should read the
crontab from stdin. See

    http://pubs.opengroup.org/onlinepubs/9699919799/utilities/crontab.html

Fix provided by TANIGUCHI Takaki <takaki@asis.media-as.org>.

Bug-Debian: https://bugs.debian.org/514062
Forwarded: no
Last-Update: 2016-01-15
Index: cron/crontab.c
===================================================================
--- cron.orig/crontab.c
+++ cron/crontab.c
@@ -106,6 +106,9 @@ main(argc, argv)
 #if defined(BSD)
 	setlinebuf(stderr);
 #endif
+	if (argv[1] == NULL) {
+		argv[1] = "-";
+	}
 	parse_args(argc, argv);		/* sets many globals, opens a file */
 	set_cron_uid();
 	set_cron_cwd();