nixos/systemd: Allow creation of unit directories

This patch allows creation of files like
/etc/systemd/system/user-.slice.d/limits.conf with

    systemd.units."user-.slice.d/limits.conf" = {
      text = ''
        [Slice]
        CPUAccounting=yes
        CPUQuota=50%
      '';
    };

which previously threw an error

Also renames the systemd-unit-path test to sytsemd-misc, and extends it to
test that `systemd.units` can handle directories. In this case we make
sure that resource limits specified in user slices apply.

nixos/lib/systemd-lib.nix

@@ -23,8 +23,9 @@ in rec {
           inherit (unit) text;
         }
         ''
-          mkdir -p $out
+          name=${shellEscape name}
-          echo -n "$text" > $out/${shellEscape name}
+          mkdir -p "$out/$(dirname "$name")"
+          echo -n "$text" > "$out/$name"
         ''
     else
       pkgs.runCommand "unit-${mkPathSafeName name}-disabled"
@@ -32,8 +33,9 @@ in rec {
           allowSubstitutes = false;
         }
         ''
-          mkdir -p $out
+          name=${shellEscape name}
-          ln -s /dev/null $out/${shellEscape name}
+          mkdir -p "$out/$(dirname "$name")"
+          ln -s /dev/null "$out/$name"
         '';
 
   boolValues = [true false "yes" "no"];

nixos/tests/all-tests.nix

@@ -518,7 +518,7 @@ in
   systemd-networkd-vrf = handleTest ./systemd-networkd-vrf.nix {};
   systemd-nspawn = handleTest ./systemd-nspawn.nix {};
   systemd-timesyncd = handleTest ./systemd-timesyncd.nix {};
-  systemd-unit-path = handleTest ./systemd-unit-path.nix {};
+  systemd-misc = handleTest ./systemd-misc.nix {};
   taskserver = handleTest ./taskserver.nix {};
   teeworlds = handleTest ./teeworlds.nix {};
   telegraf = handleTest ./telegraf.nix {};

nixos/tests/systemd-misc.nix

@@ -29,10 +29,23 @@ let
   };
 in
 {
-  name = "systemd-unit-path";
+  name = "systemd-misc";
 
   machine = { pkgs, lib, ... }: {
     boot.extraSystemdUnitPaths = [ "/etc/systemd-rw/system" ];
+
+    users.users.limited = {
+      isNormalUser = true;
+      uid = 1000;
+    };
+
+    systemd.units."user-1000.slice.d/limits.conf" = {
+      text = ''
+        [Slice]
+        TasksAccounting=yes
+        TasksMax=100
+      '';
+    };
   };
 
   testScript = ''
@@ -43,5 +56,7 @@ in
     )
     machine.succeed("systemctl start example.service")
     machine.succeed("systemctl status example.service | grep 'Active: active'")
+
+    machine.succeed("systemctl show --property TasksMax --value user-1000.slice | grep 100")
   '';
 })