[dm-constraints] Automatically add constraints to all models when req…

…uired

* This change is consistent with behavior of other DM plugins.
* Minor doc update to show that intermediaries inherit constraints from
  the anonymous m:m relationships.

[#1078 state:resolved]

dm-constraints/README.rdoc

@@ -42,10 +42,14 @@ end
 class Articles
   has n, :tags, :through => Resource, :constraint => :destroy
 end
+
 class Tags
   has n, :articles, :through => Resource, :constraint => :destroy
 end
 
+# Intermediary constraints for relationships using :through => Resource
+# are automatically inherited from the M:M relationship.
+
 # 1:1 Example
 class Farmer
   has 1, :beloved_sheep, :constraint => :protect

dm-constraints/lib/dm-constraints.rb

@@ -57,6 +57,8 @@ def self.included(model)
         end
       RUBY
     end
+
+    Model.append_inclusions self
   end
 
   module Migrations

dm-constraints/spec/integration/constraints_spec.rb

@@ -8,7 +8,6 @@
 
       class ::Article
         include DataMapper::Resource
-        include DataMapper::Constraints
 
         property :id,      Serial
         property :title,   String, :nullable => false
@@ -21,7 +20,6 @@ class ::Article
 
       class ::Author
         include DataMapper::Resource
-        include DataMapper::Constraints
 
         property :first_name, String, :key => true
         property :last_name,  String, :key => true
@@ -32,7 +30,6 @@ class ::Author
 
       class ::Comment
         include DataMapper::Resource
-        include DataMapper::Constraints
 
         property :id,   Serial
         property :body, Text
@@ -45,7 +42,6 @@ class ::Comment
       # on the other end
       class ::Revision
         include DataMapper::Resource
-        include DataMapper::Constraints
 
         property :id,   Serial
         property :text, String