Index: db/migrate/091_change_changesets_revision_to_string.rb
===================================================================
--- db/migrate/091_change_changesets_revision_to_string.rb	(revision 1709)
+++ db/migrate/091_change_changesets_revision_to_string.rb	(working copy)
@@ -1,9 +1,15 @@
 class ChangeChangesetsRevisionToString < ActiveRecord::Migration
   def self.up
+    remove_index :changesets, :name => :changesets_repos_rev
     change_column :changesets, :revision, :string, :null => false
+    add_index :changesets, [:repository_id, :revision], :unique => true, :name => :changesets_repos_rev
+    
   end
 
   def self.down
+    remove_index :changesets, :name => :changesets_repos_rev
     change_column :changesets, :revision, :integer, :null => false
+    add_index :changesets, [:repository_id, :revision], :unique => true, :name => :changesets_repos_rev
+
   end
 end
Index: db/migrate/092_change_changes_from_revision_to_string.rb
===================================================================
--- db/migrate/092_change_changes_from_revision_to_string.rb	(revision 1709)
+++ db/migrate/092_change_changes_from_revision_to_string.rb	(working copy)
@@ -1,9 +1,9 @@
 class ChangeChangesFromRevisionToString < ActiveRecord::Migration
   def self.up
-    change_column :changes, :from_revision, :string
+    change_column :changes, :from_revision, :string, :default => nil
   end
 
   def self.down
-    change_column :changes, :from_revision, :integer
+    change_column :changes, :from_revision, :integer, :default => nil
   end
 end