Force the default value of path to be set on the Change model class. This is needed because MySQL does not support default values on text columns (Error introduced in r3828, #5771)

app/models/change.rb

@@ -23,4 +23,8 @@ class Change < ActiveRecord::Base
   def relative_path
     changeset.repository.relative_path(path)
   end
+  
+  def before_save
+    path ||= ""
+  end
 end

db/migrate/20100705164950_change_changes_path_length_limit.rb

@@ -1,6 +1,6 @@
 class ChangeChangesPathLengthLimit < ActiveRecord::Migration
   def self.up
-    change_column :changes, :path, :text, :default => "", :null => false
+    change_column :changes, :path, :text, :null => false
     change_column :changes, :from_path, :text
   end