Added upgrade notes for 1.5 to 2.0

book/51_upgrading

@@ -1,5 +1,93 @@
 = Appendix I: Upgrade Notes
 
 == From 1.5 to 2.0
+=== Rack
 
-TODO
+The biggest change in 2.0 is that it now uses Rack[http://rack.rubyforge.org/]
+internally. This means that you'll now have to deploy Camping differently, but
+hopefully more easily too. Now every Camping application is also a Rack
+application, so simply check out the documentation to the server of your
+choice.
+
+=== require 'camping/db'
+
+In earlier versions of Camping, you loaded database support by:
+
+  require 'camping/db'
+
+Actually, this loaded a very thin layer on top of ActiveRecord, and in the
+future we want to experiment with other libraries. Therefore you should now
+simply remove the line, and instead just inherit from Base right away. This
+also means you'll have to place your migrations *after* the models.
+
+We also encourage you to use <tt>Model.table_name</tt> instead of
+<tt>:appname_model</tt>, just to make sure it's named correctly.
+
+  ## Don't require anything:
+  # require 'camping/db'
+
+  module Nuts::Models
+    ## Just inherit Base:
+    class Page < Base; end
+
+    ## Migrations have to come *after* the models:
+    class CreateTheBasics < V 0.1
+      def self.up
+        create_table Page.table_name do |t|
+          ...
+        end
+      end
+
+      def self.down
+        drop_table Page.table_name
+      end
+    end
+  end
+
+=== Cookie Sessions
+
+Camping 2.0 now uses a cookie-based session system, which means you now longer
+need a database in order to use sessions. The disadvantage of this is that
+you are restricted to only around 4k of data. See below for the changes
+required, and see Camping::Session more details.
+
+  module Nuts
+    ## Include Camping::Session as before:
+    include Camping::Session
+
+    ## But also define a secret:
+    secret "Very secret text, which no-one else should know!"
+  end
+
+  def Nuts.create
+    ## And remove the following line:
+    # Camping::Models::Session.create_schema
+  end
+
+===  Error handling
+
+Camping now uses three methods in order to handle errors. These replaces the
+old classes NotFound and ServerError.
+
+* Camping::Base#r404 is called when a route can't be found.
+* Camping::Base#r501 is called when a route is found, but doesn't respond to 
+  the method.
+* Camping::Base#r500 is called when an error happens.
+
+You can override these in your application:
+
+  module Nuts
+    def r404(path)
+      "Sorry, but I can't find #{path}."
+    end
+
+    def r501(method)
+      "Sorry, but I can't respond to #{method}."
+    end
+
+    def r500(klass, method, ex)
+      "Sorry, but #{klass}##{method} failed with #{ex}."
+    end
+  end
+
+It should be noted that this might change in the future.