mtail: fix getting logs from STDIN

CHANGELOG.md

@@ -2,6 +2,9 @@
 
 ## untagged
 
+- mtail: fix getting logs from STDIN
+  ([#502](https://github.com/chatmail/chatmail/pull/502))
+
 - filtermail: don't require exactly 2 lines after openPGP payload
   ([#497](https://github.com/chatmail/chatmail/pull/497))
 

cmdeploy/src/cmdeploy/mtail/mtail.service.j2

@@ -3,7 +3,7 @@ Description=mtail
 
 [Service]
 Type=simple
-ExecStart=/bin/sh -c "journalctl -f -o short-iso -n 0 | /usr/bin/mtail --address={{ address }} --port={{ port }} --progs /etc/mtail --logtostderr --logs -"
+ExecStart=/bin/sh -c "journalctl -f -o short-iso -n 0 | /usr/bin/mtail --address={{ address }} --port={{ port }} --progs /etc/mtail --logtostderr --logs /dev/stdin"
 Restart=on-failure
 
 [Install]