convert mount service to trigger

Good: this means it's not hanging holding the s6 dataase lock.

Bad: it's the ugliest implementation and doesn't deserve to be preserved

(tbf the ugliness is not new)

modules/mount/service.nix

@@ -4,15 +4,28 @@
 }:
 { device, mountpoint, options, fstype }:
 let
-  inherit (liminix.services) oneshot;
-in oneshot {
-  name = "mount.${lib.escapeURL mountpoint}";
-  up = ''
+  inherit (liminix.services) longrun oneshot;
+  options_string =
+    if options == [] then "" else "-o ${lib.concatStringsSep "," options}";
+  mount_service = oneshot {
+    name = "mount.${lib.escapeURL mountpoint}";
+    timeout-up = 3600;
+    up = "mount -t ${fstype} ${options_string} ${device} ${mountpoint}";
+    down = "umount ${mountpoint}";
+  };
+in longrun {
+  name = "watch-mount.${lib.strings.sanitizeDerivationName mountpoint}";
+  isTrigger = true;
+  buildInputs = [ mount_service ];
+
+  # This accommodates bringing the service up when the device appears.
+  # It doesn't bring it down on unplug because unmount will probably
+  # fail anyway (so don't do that)
+  run = ''
     while ! findfs ${device}; do
       echo waiting for device ${device}
       sleep 1
     done
-    mount -t ${fstype} -o ${lib.concatStringsSep "," options} ${device} ${mountpoint}
+    s6-rc -b -u change ${mount_service.name}
   '';
-  down = "umount ${mountpoint}";
 }