Index: app/models/change.rb
===================================================================
--- app/models/change.rb	(revision 3859)
+++ app/models/change.rb	(working copy)
@@ -19,12 +19,13 @@
   belongs_to :changeset
   
   validates_presence_of :changeset_id, :action, :path
+  before_save :init_path
   
   def relative_path
     changeset.repository.relative_path(path)
   end
   
-  def before_save
-    path ||= ""
+  def init_path
+    self.path ||= ""
   end
 end
Index: db/migrate/20100705164950_change_changes_path_length_limit.rb
===================================================================
--- db/migrate/20100705164950_change_changes_path_length_limit.rb	(revision 3859)
+++ db/migrate/20100705164950_change_changes_path_length_limit.rb	(working copy)
@@ -1,6 +1,9 @@
 class ChangeChangesPathLengthLimit < ActiveRecord::Migration
   def self.up
+    # these are two steps to please MySQL 5 on Win32
+    change_column :changes, :path, :text, :default => nil, :null => true
     change_column :changes, :path, :text, :null => false
+    
     change_column :changes, :from_path, :text
   end