lxc-create: Require --template be passed

doc/lxc-create.sgml.in

@@ -115,6 +115,7 @@ Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 	    for details of the expected script structure.
 	    Alternatively, the full path to an executable template script
 	    can also be passed as a parameter.
+	    "none" can be used to force lxc-create to skip rootfs creation.
 	  </para>
 	</listitem>
       </varlistentry>

src/lxc/lxc_create.c

@@ -132,7 +132,7 @@ static struct lxc_arguments my_args = {
 	.progname = "lxc-create",
 	.helpfn   = create_helpfn,
 	.help     = "\
---name=NAME [-w] [-r] [-t template] [-P lxcpath]\n\
+--name=NAME -t template [-w] [-r] [-P lxcpath]\n\
 \n\
 lxc-create creates a container\n\
 \n\
@@ -203,6 +203,15 @@ int main(int argc, char *argv[])
 		exit(1);
 	lxc_log_options_no_override();
 
+	if (!my_args.template) {
+		fprintf(stderr, "A template must be specified.\n");
+		fprintf(stderr, "Use \"none\" if you really want a container without a rootfs.\n");
+		exit(1);
+	}
+
+	if (strcmp(my_args.template, "none") == 0)
+		my_args.template = NULL;
+
 	memset(&spec, 0, sizeof(spec));
 	if (!my_args.bdevtype)
 		my_args.bdevtype = "_unset";