nix: configure sharefs as a mount unit

This should have been configured via fileSystem instead, but that somehow has no effect, it is not even being evaluated, and I am not wasting any more time on nix. This change aims to keep everything working until all nix/systemd tooling is replaced.

Signed-off-by: Ophestra <cat@gensokyo.uk>

nixos.nix

@@ -66,42 +66,56 @@ in
       ) "" cfg.users;
     };
 
+    environment.systemPackages = optional (cfg.sharefs.source != null) cfg.sharefs.package;
+
     systemd.services = {
-      sharefs = mkIf (cfg.sharefs.source != null) {
-        unitConfig.RequiresMountsFor = cfg.sharefs.source;
+      sharefs-setup = mkIf (cfg.sharefs.source != null) {
+        unitConfig.RequiresMountsFor = dirOf cfg.sharefs.source;
         serviceConfig = {
-          NoNewPrivileges = true;
+          Type = "oneshot";
+          RemainAfterExit = true;
         };
         script = ''
           ${pkgs.coreutils}/bin/install \
             -dm0700 \
             -o ${cfg.sharefs.user} \
             -g ${cfg.sharefs.group} \
-            ${cfg.sharefs.source} ${cfg.sharefs.name}
-
-          exec ${cfg.package}/libexec/sharefs -f \
-            -o ${
-              lib.join "," [
-                "noexec"
-                "nosuid"
-                "nodev"
-                "noatime"
-                "auto_unmount"
-                "allow_other"
-                "setuid=$(id -u ${cfg.sharefs.user})"
-                "setgid=$(id -g ${cfg.sharefs.group})"
-                "source=${cfg.sharefs.source}"
-              ]
-            } ${cfg.sharefs.name}
+            ${cfg.sharefs.source}
         '';
-
-        # do not unmount on configuration changes
-        restartIfChanged = false;
-
-        wantedBy = [ "multi-user.target" ];
+        wantedBy = [ "local-fs.target" ];
       };
     };
 
+    systemd.mounts = optional (cfg.sharefs.source != null) {
+      unitConfig.RequiresMountsFor = cfg.sharefs.source;
+      where = cfg.sharefs.name;
+      what = "sharefs";
+      type = "fuse.sharefs";
+      options = lib.join "," [
+        "noexec"
+        "nosuid"
+        "nodev"
+        "noatime"
+        "auto_unmount"
+        "allow_other"
+        "setuid=${toString config.users.users.${cfg.sharefs.user}.uid}"
+        "setgid=${toString config.users.groups.${cfg.sharefs.group}.gid}"
+        "source=${cfg.sharefs.source}"
+      ];
+      wants = [ "sharefs-setup.service" ];
+      after = [ "sharefs-setup.service" ];
+      before = [
+        "local-fs.target"
+        "multi-user.target"
+        "nix-daemon.socket"
+      ];
+      wantedBy = [
+        "local-fs.target"
+        "multi-user.target"
+        "nix-daemon.socket"
+      ];
+    };
+
     home-manager =
       let
         privPackages = mapAttrs (_: userid: {