Show the "Btrfs subvolume" option when creating a user

Which will allow to create the user home as a btrfs subvolume instead as
a plain dir.

src/include/users/dialogs.rb

@@ -27,6 +27,7 @@
 #
 # $Id$
 
+require "pathname"
 require "shellwords"
 
 require "users/ssh_public_key"
@@ -64,6 +65,21 @@ def initialize_users_dialogs(include_target)
       @default_pw = "******"
     end
 
+    def btrfs_path?(path)
+      dirname = Pathname.new(path).dirname
+      fstype = Yast::Execute.locally!.stdout("/usr/bin/stat", "-f", "--format", "%T", dirname).chomp
+
+      fstype == "btrfs"
+    end
+
+    def redraw_btrfs_subvolume_option
+      home_dir = UI.QueryWidget(Id(:home), :Value)
+      valid_btrfs_path = btrfs_path?(home_dir)
+
+      UI.ChangeWidget(Id(:btrfs_subvolume), :Enabled, valid_btrfs_path)
+      UI.ChangeWidget(Id(:btrfs_subvolume), :Value, false) unless valid_btrfs_path
+    end
+
     # Uppercase letters were used in username! (see bug #26409)
     # In these popups, ask user what to do.
     def AskForUppercasePopup(username)
@@ -389,6 +405,7 @@ def EditUserDialog(what)
       create_home = Ops.get_boolean(user, "create_home", true)
       chown_home = Ops.get_boolean(user, "chown_home", true)
       no_skel = Ops.get_boolean(user, "no_skeleton", false)
+      btrfs_subvolume = Ops.get_boolean(user, "btrfs_subvolume", false)
       do_not_edit = user_type == "nis"
 
       complex_layout = installation && Users.StartDialog("user_add")
@@ -462,6 +479,7 @@ def EditUserDialog(what)
 
         chown_home = Ops.get_boolean(user, "chown_home", chown_home)
         no_skel = Ops.get_boolean(user, "no_skeleton", no_skel)
+        btrfs_subvolume = Ops.get_boolean(user, "btrfs_subvolume", btrfs_subvolume)
         groups = Ops.get_map(user, "grouplist", {})
         do_not_edit = user_type == "nis"
 
@@ -724,7 +742,7 @@ def EditUserDialog(what)
 
         home_w = VBox(
           # textentry label
-          InputField(Id(:home), Opt(:hstretch), _("&Home Directory"), home),
+          InputField(Id(:home), Opt(:hstretch, :notify), _("&Home Directory"), home),
           action != "edited" ?
             Empty() :
             HBox(
@@ -753,6 +771,10 @@ def EditUserDialog(what)
             HBox(
               HSpacing(),
               Left(CheckBox(Id(:skel), _("E&mpty Home"), no_skel))
+            ),
+            HBox(
+              HSpacing(),
+              Left(CheckBox(Id(:btrfs_subvolume), _("Btrfs subvolume"), btrfs_subvolume))
             )
           )
 
@@ -1011,6 +1033,12 @@ def EditUserDialog(what)
         error = ""
 
         ret = Convert.to_symbol(UI.UserInput) if current != nil
+
+        if ret == :home
+          redraw_btrfs_subvolume_option
+          next
+        end
+
         if (ret == :abort || ret == :cancel) && ReallyAbort() != :abort
           ret = :notnext
           next
@@ -1342,6 +1370,7 @@ def EditUserDialog(what)
               )
             end
             UI.ChangeWidget(Id(:home), :Value, dir)
+            redraw_btrfs_subvolume_option
           end
         end
 
@@ -1355,6 +1384,7 @@ def EditUserDialog(what)
           new_home = Convert.to_string(UI.QueryWidget(Id(:home), :Value))
 
           if what == "add_user"
+            btrfs_subvolume = UI.QueryWidget(Id(:btrfs_subvolume), :Enabled) && UI.QueryWidget(Id(:btrfs_subvolume), :Value)
             no_skel = Convert.to_boolean(UI.QueryWidget(Id(:skel), :Value))
             mode = Convert.to_string(UI.QueryWidget(Id(:mode), :Value))
           end
@@ -1539,6 +1569,7 @@ def EditUserDialog(what)
           Ops.set(user, "addit_data", addit_data)
           Ops.set(user, "no_skeleton", no_skel)
           Ops.set(user, "home_mode", mode)
+          Ops.set(user, "btrfs_subvolume", btrfs_subvolume)
         end
 
         if current == :passwordsettings && (ret == :next || tab)