Added some documentation about setting :autosave => false on an association.

activerecord/lib/active_record/associations.rb

@@ -280,9 +280,10 @@ def association_instance_set(name, association)
     # You can manipulate objects and associations before they are saved to the database, but there is some special behavior you should be
     # aware of, mostly involving the saving of associated objects.
     #
-    # Unless you enable the :autosave option on a <tt>has_one</tt>, <tt>belongs_to</tt>,
-    # <tt>has_many</tt>, or <tt>has_and_belongs_to_many</tt> association,
-    # in which case the members are always saved.
+    # Unless you set the :autosave option on a <tt>has_one</tt>, <tt>belongs_to</tt>,
+    # <tt>has_many</tt>, or <tt>has_and_belongs_to_many</tt> association. Setting it
+    # to +true+ will _always_ save the members, whereas setting it to +false+ will
+    # _never_ save the members.
     #
     # === One-to-one associations
     #