nixos/udisks2: add mountOnMedia option

nixos/modules/services/hardware/udisks2.nix

@@ -1,10 +1,9 @@
 # Udisks daemon.
-
 { config, lib, pkgs, ... }:
-
 with lib;
 
 let
+  cfg = config.services.udisks2;
   settingsFormat = pkgs.formats.ini {
     listToValue = concatMapStringsSep "," (generators.mkValueStringDefault {});
   };
@@ -19,7 +18,17 @@ in
 
     services.udisks2 = {
 
-      enable = mkEnableOption (lib.mdDoc "udisks2, a DBus service that allows applications to query and manipulate storage devices");
+      enable = mkEnableOption (mdDoc "udisks2, a DBus service that allows applications to query and manipulate storage devices");
+
+      mountOnMedia = mkOption {
+        type = types.bool;
+        default = false;
+        description = mdDoc ''
+          When enabled, instructs udisks2 to mount removable drives under `/media/` directory, instead of the
+          default, ACL-controlled `/run/media/$USER/`. Since `/media/` is not mounted as tmpfs by default, it
+          requires cleanup to get rid of stale mountpoints; enabling this option will take care of this at boot.
+        '';
+      };
 
       settings = mkOption rec {
         type = types.attrsOf settingsFormat.type;
@@ -44,7 +53,7 @@ in
           };
         };
         '';
-        description = lib.mdDoc ''
+        description = mdDoc ''
           Options passed to udisksd.
           See [here](http://manpages.ubuntu.com/manpages/latest/en/man5/udisks2.conf.5.html) and
           drive configuration in [here](http://manpages.ubuntu.com/manpages/latest/en/man8/udisks.8.html) for supported options.
@@ -73,10 +82,15 @@ in
 
     services.dbus.packages = [ pkgs.udisks2 ];
 
-    systemd.tmpfiles.rules = [ "d /var/lib/udisks2 0755 root root -" ];
+    systemd.tmpfiles.rules = [ "d /var/lib/udisks2 0755 root root -" ]
+      ++ optional cfg.mountOnMedia "D! /media 0755 root root -";
 
     services.udev.packages = [ pkgs.udisks2 ];
 
+    services.udev.extraRules = optionalString cfg.mountOnMedia ''
+      ENV{ID_FS_USAGE}=="filesystem", ENV{UDISKS_FILESYSTEM_SHARED}="1"
+    '';
+
     systemd.packages = [ pkgs.udisks2 ];
   };