Force-clear the default value for migration from :string to :text. #5846 #5771

This is a special case for MySQL in Win32.

Contributed by Holger Just.

git-svn-id: svn+ssh://rubyforge.org/var/svn/redmine/trunk@3860 e93f8b46-1217-0410-a6f0-8f06a7374b81

db/migrate/20100705164950_change_changes_path_length_limit.rb

@@ -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