Show the records in Relation#inspect

The reason for removing the previous implementation of `#inspect` was
that it hid from you that you were dealing with a `Relation` rather than
an `Array`.

But it is still useful to be able to see the records, particularly if you're
writing something like the following in tests:

    assert_equal [foo], Post.where(:bar)

If the assertion fails, you want to see what records were actually
loaded.

So this implementation makes it clear that you've got a `Relation`, but
also shows your records.

activerecord/CHANGELOG.md

@@ -20,14 +20,16 @@
 
     *Aleksey Magusev*
 
-*   `ActiveRelation#inspect` no longer calls `#to_a`. This means that in places
-    where `#inspect` is implied (such as in the console), creating a relation
-    will not execute it anymore, you'll have to call `#to_a` when necessary:
+*   `ActiveRecord::Relation#inspect` now makes it clear that you are
+    dealing with a `Relation` object rather than an array:.
 
-       User.where(:age => 30)      # => returns the relation
-       User.where(:age => 30).to_a # => executes the query and returns the loaded objects, as before
+       User.where(:age => 30).inspect
+       # => <ActiveRecord::Relation [#<User ...>, #<User ...>]>
 
-    *Brian Cardarella*
+       User.where(:age => 30).to_a.inspect
+       # => [#<User ...>, #<User ...>]
+
+    *Brian Cardarella & Jon Leighton*
 
 *   Add `collation` and `ctype` support to PostgreSQL. These are available for PostgreSQL 8.4 or later.
     Example:

activerecord/lib/active_record/relation.rb

@@ -514,6 +514,10 @@ module ActiveRecord
       @values.dup
     end
 
+    def inspect
+      "#<#{self.class.name} #{to_a.inspect}>"
+    end
+
     private
 
     def references_eager_loaded_tables?

activerecord/test/cases/relations_test.rb

@@ -1311,4 +1311,9 @@ class RelationTest < ActiveRecord::TestCase
       relation.merge! where: 'foo'
     end
   end
+
+  test "relations show the records in #inspect" do
+    relation = Post.limit(2)
+    assert_equal "#<ActiveRecord::Relation [#{Post.limit(2).map(&:inspect).join(', ')}]>", relation.inspect
+  end
 end