allow setting service name from command arguments

sys/man/4/cwfs

@@ -6,6 +6,9 @@ cwfs \- cached-worm file server, dump
 [
 .B -csC
 ] [
+.B -n
+.I service
+] [
 .B -a
 .I announce-string
 ] ... [
@@ -91,6 +94,11 @@ thereafter.
 enter the file server's configuration mode
 before starting normal operation.
 .TP
+.B -n
+overrides the 
+.I service
+name of the file server's configuration.
+.TP
 .B -s
 Post file descriptor zero in
 .BI /srv/ service

sys/src/cmd/cwfs/main.c

@@ -279,7 +279,7 @@ printsizes(void)
 void
 usage(void)
 {
-	fprint(2, "usage: %s [ -csC ] [ -a ann-str ] [ -m dev-map ] [-f config-dev ]\n", argv0);
+	fprint(2, "usage: %s [ -csC ] [-n service] [ -a ann-str ] [ -m dev-map ] [-f config-dev ]\n", argv0);
 	exits("usage");
 }
 
@@ -306,6 +306,9 @@ main(int argc, char **argv)
 		}
 		annstrs[nets++] = ann;
 		break;
+	case 'n':
+		strcpy(service, EARGF(usage()));
+		break;
 	case 's':
 		sfd = dup(0, -1);
 		rfd = dup(1, -1);