Fixes old migrations w/ trackers.

This adds the old tracker model to the migrations that use it. The code
for the migrations was not changed, as the const name is set to Tracker
via

  Object.const_set("Tracker", AddTrackerPosition::Tracker)

Each migration removes the Tracker constant afterwards with

  Object.send(:remove_const, :Tracker)

db/migrate/021_add_tracker_position.rb

@@ -11,9 +11,65 @@
 #++
 
 class AddTrackerPosition < ActiveRecord::Migration
+
+  class Tracker < ActiveRecord::Base
+    before_destroy :check_integrity
+    has_many :issues
+    has_many :workflows, :dependent => :delete_all do
+      def copy(source_tracker)
+        Workflow.copy(source_tracker, nil, proxy_association.owner, nil)
+      end
+    end
+
+    has_and_belongs_to_many :projects
+    has_and_belongs_to_many :custom_fields, :class_name => 'WorkPackageCustomField', :join_table => "#{table_name_prefix}custom_fields_trackers#{table_name_suffix}", :association_foreign_key => 'custom_field_id'
+    acts_as_list
+
+    validates_presence_of :name
+    validates_uniqueness_of :name
+    validates_length_of :name, :maximum => 30
+
+    def to_s; name end
+
+    def <=>(tracker)
+      name <=> tracker.name
+    end
+
+    def self.all
+      find(:all, :order => 'position')
+    end
+
+    # Returns an array of IssueStatus that are used
+    # in the tracker's workflows
+    def issue_statuses
+      if @issue_statuses
+        return @issue_statuses
+      elsif new_record?
+        return []
+      end
+
+      ids = Workflow.
+              connection.select_rows("SELECT DISTINCT old_status_id, new_status_id FROM #{Workflow.table_name} WHERE tracker_id = #{id}").
+              flatten.
+              uniq
+
+      @issue_statuses = IssueStatus.find_all_by_id(ids).sort
+    end
+
+  private
+    def check_integrity
+      raise "Can't delete tracker" if Issue.find(:first, :conditions => ["tracker_id=?", self.id])
+    end
+  end
+
   def self.up
+
+    Object.const_set("Tracker", AddTrackerPosition::Tracker)
+
     add_column :trackers, :position, :integer, :default => 1
     Tracker.find(:all).each_with_index {|tracker, i| tracker.update_attribute(:position, i+1)}
+
+    Object.send(:remove_const, :Tracker)
   end
 
   def self.down

db/migrate/081_create_projects_trackers.rb

@@ -11,7 +11,61 @@
 #++
 
 class CreateProjectsTrackers < ActiveRecord::Migration
+
+  class Tracker < ActiveRecord::Base
+    before_destroy :check_integrity
+    has_many :issues
+    has_many :workflows, :dependent => :delete_all do
+      def copy(source_tracker)
+        Workflow.copy(source_tracker, nil, proxy_association.owner, nil)
+      end
+    end
+
+    has_and_belongs_to_many :projects
+    has_and_belongs_to_many :custom_fields, :class_name => 'WorkPackageCustomField', :join_table => "#{table_name_prefix}custom_fields_trackers#{table_name_suffix}", :association_foreign_key => 'custom_field_id'
+    acts_as_list
+
+    validates_presence_of :name
+    validates_uniqueness_of :name
+    validates_length_of :name, :maximum => 30
+
+    def to_s; name end
+
+    def <=>(tracker)
+      name <=> tracker.name
+    end
+
+    def self.all
+      find(:all, :order => 'position')
+    end
+
+    # Returns an array of IssueStatus that are used
+    # in the tracker's workflows
+    def issue_statuses
+      if @issue_statuses
+        return @issue_statuses
+      elsif new_record?
+        return []
+      end
+
+      ids = Workflow.
+              connection.select_rows("SELECT DISTINCT old_status_id, new_status_id FROM #{Workflow.table_name} WHERE tracker_id = #{id}").
+              flatten.
+              uniq
+
+      @issue_statuses = IssueStatus.find_all_by_id(ids).sort
+    end
+
+  private
+    def check_integrity
+      raise "Can't delete tracker" if Issue.find(:first, :conditions => ["tracker_id=?", self.id])
+    end
+  end
+
   def self.up
+
+    Object.const_set("Tracker", AddTrackerPosition::Tracker)
+
     create_table :projects_trackers, :id => false do |t|
       t.column :project_id, :integer, :default => 0, :null => false
       t.column :tracker_id, :integer, :default => 0, :null => false
@@ -23,6 +77,8 @@ class CreateProjectsTrackers < ActiveRecord::Migration
     Project.find(:all).each do |project|
       project.tracker_ids = tracker_ids
     end
+
+    Object.send(:remove_const, :Tracker)
   end
 
   def self.down