uboot: (firmwareOdroidC2/C4) don't invoke patch tool, use patches = [] instead

https://github.com/NixOS/nixpkgs/blob/master/pkgs/stdenv/generic/setup.sh#L948
this can do it nicely.

Signed-off-by: Anton Arapov <anton@deadbeef.mx>

nixos/modules/services/misc/snapper.nix

@@ -0,0 +1,187 @@
+{ config, pkgs, lib, ... }:
+
+with lib;
+
+let
+  cfg = config.services.snapper;
+in
+
+{
+  options.services.snapper = {
+
+    snapshotRootOnBoot = mkOption {
+      type = types.bool;
+      default = false;
+      description = ''
+        Whether to snapshot root on boot
+      '';
+    };
+
+    snapshotInterval = mkOption {
+      type = types.str;
+      default = "hourly";
+      description = ''
+        Snapshot interval.
+
+        The format is described in
+        <citerefentry><refentrytitle>systemd.time</refentrytitle>
+        <manvolnum>7</manvolnum></citerefentry>.
+      '';
+    };
+
+    cleanupInterval = mkOption {
+      type = types.str;
+      default = "1d";
+      description = ''
+        Cleanup interval.
+
+        The format is described in
+        <citerefentry><refentrytitle>systemd.time</refentrytitle>
+        <manvolnum>7</manvolnum></citerefentry>.
+      '';
+    };
+
+    filters = mkOption {
+      type = types.nullOr types.lines;
+      default = null;
+      description = ''
+        Global display difference filter. See man:snapper(8) for more details.
+      '';
+    };
+
+    configs = mkOption {
+      default = { };
+      example = literalExpression ''
+        {
+          home = {
+            subvolume = "/home";
+            extraConfig = '''
+              ALLOW_USERS="alice"
+              TIMELINE_CREATE=yes
+              TIMELINE_CLEANUP=yes
+            ''';
+          };
+        }
+      '';
+
+      description = ''
+        Subvolume configuration
+      '';
+
+      type = types.attrsOf (types.submodule {
+        options = {
+          subvolume = mkOption {
+            type = types.path;
+            description = ''
+              Path of the subvolume or mount point.
+              This path is a subvolume and has to contain a subvolume named
+              .snapshots.
+              See also man:snapper(8) section PERMISSIONS.
+            '';
+          };
+
+          fstype = mkOption {
+            type = types.enum [ "btrfs" ];
+            default = "btrfs";
+            description = ''
+              Filesystem type. Only btrfs is stable and tested.
+            '';
+          };
+
+          extraConfig = mkOption {
+            type = types.lines;
+            default = "";
+            description = ''
+              Additional configuration next to SUBVOLUME and FSTYPE.
+              See man:snapper-configs(5).
+            '';
+          };
+        };
+      });
+    };
+  };
+
+  config = mkIf (cfg.configs != {}) (let
+    documentation = [ "man:snapper(8)" "man:snapper-configs(5)" ];
+  in {
+
+    environment = {
+
+      systemPackages = [ pkgs.snapper ];
+
+      # Note: snapper/config-templates/default is only needed for create-config
+      #       which is not the NixOS way to configure.
+      etc = {
+
+        "sysconfig/snapper".text = ''
+          SNAPPER_CONFIGS="${lib.concatStringsSep " " (builtins.attrNames cfg.configs)}"
+        '';
+
+      }
+      // (mapAttrs' (name: subvolume: nameValuePair "snapper/configs/${name}" ({
+        text = ''
+          ${subvolume.extraConfig}
+          FSTYPE="${subvolume.fstype}"
+          SUBVOLUME="${subvolume.subvolume}"
+        '';
+      })) cfg.configs)
+      // (lib.optionalAttrs (cfg.filters != null) {
+        "snapper/filters/default.txt".text = cfg.filters;
+      });
+
+    };
+
+    services.dbus.packages = [ pkgs.snapper ];
+
+    systemd.services.snapperd = {
+      description = "DBus interface for snapper";
+      inherit documentation;
+      serviceConfig = {
+        Type = "dbus";
+        BusName = "org.opensuse.Snapper";
+        ExecStart = "${pkgs.snapper}/bin/snapperd";
+        CapabilityBoundingSet = "CAP_DAC_OVERRIDE CAP_FOWNER CAP_CHOWN CAP_FSETID CAP_SETFCAP CAP_SYS_ADMIN CAP_SYS_MODULE CAP_IPC_LOCK CAP_SYS_NICE";
+        LockPersonality = true;
+        NoNewPrivileges = false;
+        PrivateNetwork = true;
+        ProtectHostname = true;
+        RestrictAddressFamilies = "AF_UNIX";
+        RestrictRealtime = true;
+      };
+    };
+
+    systemd.services.snapper-timeline = {
+      description = "Timeline of Snapper Snapshots";
+      inherit documentation;
+      requires = [ "local-fs.target" ];
+      serviceConfig.ExecStart = "${pkgs.snapper}/lib/snapper/systemd-helper --timeline";
+      startAt = cfg.snapshotInterval;
+    };
+
+    systemd.services.snapper-cleanup = {
+      description = "Cleanup of Snapper Snapshots";
+      inherit documentation;
+      serviceConfig.ExecStart = "${pkgs.snapper}/lib/snapper/systemd-helper --cleanup";
+    };
+
+    systemd.timers.snapper-cleanup = {
+      description = "Cleanup of Snapper Snapshots";
+      inherit documentation;
+      wantedBy = [ "timers.target" ];
+      requires = [ "local-fs.target" ];
+      timerConfig.OnBootSec = "10m";
+      timerConfig.OnUnitActiveSec = cfg.cleanupInterval;
+    };
+
+    systemd.services.snapper-boot = lib.optionalAttrs cfg.snapshotRootOnBoot {
+      description = "Take snapper snapshot of root on boot";
+      inherit documentation;
+      serviceConfig.ExecStart = "${pkgs.snapper}/bin/snapper --config root create --cleanup-algorithm number --description boot";
+      serviceConfig.type = "oneshot";
+      requires = [ "local-fs.target" ];
+      wantedBy = [ "multi-user.target" ];
+      unitConfig.ConditionPathExists = "/etc/snapper/configs/root";
+    };
+
+  });
+}