mdmon: recognise --all in place of /proc/mdstat

It seems more meaningful.
Keep the old option as well for back compatibility.

Signed-off-by: NeilBrown <neilb@suse.de>

mdmon.8

@@ -129,7 +129,9 @@ CONTAINER
 The
 .B container
 device to monitor.  It can be a full path like /dev/md/container, a simple md
-device name like md127, or /proc/mdstat which tells
+device name like md127, or
+.I \-\-all
+ which tells
 .I mdmon
 to scan for containers and launch an
 .I mdmon
@@ -200,7 +202,7 @@ root filesystem.
 
 .SH EXMAPLES
 
-.B "  mdmon /proc/mdstat /"
+.B "  mdmon --all /"
 .br
 Any
 .I mdmon

mdmon.c

@@ -274,7 +274,8 @@ int main(int argc, char *argv[])
 		usage();
 	}
 
-	if (strcmp(container_name, "/proc/mdstat") == 0) {
+	if (strcmp(container_name, "/proc/mdstat") == 0 ||
+	    strcmp(container_name, "--all") == 0) {
 		struct mdstat_ent *mdstat, *e;
 
 		/* launch an mdmon instance for each container found */