scm: db: model: add parent/child relation for changesets (#5501)

Contributed by Jan Topiński.

git-svn-id: svn+ssh://rubyforge.org/var/svn/redmine/trunk@7710 e93f8b46-1217-0410-a6f0-8f06a7374b81

db/migrate/20110902000000_create_changeset_parents.rb

@@ -0,0 +1,14 @@
+class CreateChangesetParents < ActiveRecord::Migration
+  def self.up
+    create_table :changeset_parents, :id => false do |t|
+      t.column :changeset_id, :integer, :null => false
+      t.column :parent_id, :integer, :null => false
+    end
+    add_index :changeset_parents, [:changeset_id], :unique => false, :name => :changeset_parents_changeset_ids
+    add_index :changeset_parents, [:parent_id], :unique => false, :name => :changeset_parents_parent_ids
+  end
+
+  def self.down
+     drop_table :changeset_parents
+  end
+end