Use ancestry instead of acts_as_tree

See #212
Basic functionality seems ok, but specs have obviously blown up
Not sure how to make the migration pass smooth; between the first and second migration, one has to run Page.build_ancestry_from_parent_ids! which failed for me with the archive extension in place (to do with after_update calls from allowed_children_cache)

app/controllers/admin/pages_controller.rb

@@ -19,7 +19,7 @@ def message
   end
 
   def index
-    @homepage = Page.find_by_parent_id(nil)
+    @homepage = Page.root
     response_for :plural
   end
 
@@ -40,7 +40,7 @@ def assign_page_attributes
       if params[:page_id].blank?
         self.model.slug = '/'
       end
-      self.model.parent_id = params[:page_id]
+#      self.model.parent_id = params[:page_id]
     end
 
     def model_class

app/models/page.rb

@@ -1,5 +1,4 @@
-require 'acts_as_tree'
-
+# require 'acts_as_tree'
 class Page < ActiveRecord::Base
 
   class MissingRootPageError < StandardError
@@ -10,7 +9,7 @@ def initialize(message = 'Database missing root page'); super end
   before_save :update_virtual, :update_status, :set_allowed_children_cache
 
   # Associations
-  acts_as_tree :order => 'virtual DESC, title ASC'
+  # acts_as_tree :order => 'virtual DESC, title ASC'
   has_many :parts, :class_name => 'PagePart', :order => 'id', :dependent => :destroy
   accepts_nested_attributes_for :parts, :allow_destroy => true
   has_many :fields, :class_name => 'PageField', :order => 'id', :dependent => :destroy
@@ -27,10 +26,11 @@ def initialize(message = 'Database missing root page'); super end
   validates_length_of :breadcrumb, :maximum => 160
 
   validates_format_of :slug, :with => %r{^([-_.A-Za-z0-9]*|/)$}
-  validates_uniqueness_of :slug, :scope => :parent_id
+  validates_uniqueness_of :slug, :scope => :ancestry
 
   validate :valid_class_name
 
+  has_ancestry
   include Radiant::Taggable
   include StandardTags
   include DeprecatedTags
@@ -218,7 +218,7 @@ def set_allowed_children_cache
   class << self
 
     def root
-      find_by_parent_id(nil)
+      find_by_ancestry(nil)
     end
 
     def find_by_path(path, live = true)

app/models/standard_tags.rb

@@ -1224,11 +1224,11 @@ def render_children_with_pagination(tag, opts={})
       result = []
       tag.locals.previous_headers = {}
       displayed_children = paging ? findable.paginate(options.merge(paging)) : findable.all(options)
-      displayed_children.each_with_index do |item, i|
+      displayed_children.each do |item|
         tag.locals.child = item
         tag.locals.page = item
-        tag.locals.first_child = i == 0
-        tag.locals.last_child = i == displayed_children.length - 1
+        tag.locals.first_child = item == displayed_children.first
+        tag.locals.last_child = item == displayed_children.last
         result << tag.expand
       end
       if paging && displayed_children.total_pages > 1

db/20111124233701_add_ancestry_to_pages.rb

@@ -0,0 +1,11 @@
+class AddAncestryToPages < ActiveRecord::Migration
+  def self.up
+    add_column :pages, :ancestry, :string
+    add_index :pages, :ancestry
+  end
+
+  def self.down
+    remove_index :pages, :ancestry
+    remove_column :pages, :ancestry
+  end
+end

db/20111125001223_remove_parent_id_from_pages.rb

@@ -0,0 +1,11 @@
+class RemoveParentIdFromPages < ActiveRecord::Migration
+  def self.up
+    remove_index :pages, :parent_id
+    remove_column :pages, :parent_id, :integer
+  end
+
+  def self.down
+    add_column :pages, :parent_id
+    add_index :pages, :parent_id
+  end
+end

radiant.gemspec

@@ -26,6 +26,7 @@ a general purpose content managment system--not merely a blogging engine.}
   s.add_dependency "rails",         "~> 2.3.14"
   s.add_dependency "rdoc",          "~> 3.9.2"
   s.add_dependency "acts_as_tree",  "~> 0.1.1"
+  s.add_dependency "ancestry",      "~> 1.2.4"
   s.add_dependency "bundler",       ">= 1.0.0"
   s.add_dependency "compass",       "~> 0.11.1"
   s.add_dependency "delocalize",    "~> 0.2.3"