6 files changed, 56 insertions, 7 deletions
diff --git a/activesupport/CHANGELOG b/activesupport/CHANGELOG
index 59e59e37ba..1d86a2a017 100644
--- a/activesupport/CHANGELOG
+++ b/activesupport/CHANGELOG
@@ -1,5 +1,7 @@
 *SVN*
 
+* Added Hash#reverse_merge, Hash#reverse_merge!, and Hash#reverse_update to ease the use of default options
+
 * Added Array#to_sentence that'll turn ['one', 'two', 'three'] into "one, two, and three" #2157 [m.stienstra@fngtps.com]
 
 * Added Kernel#silence_warnings to turn off warnings temporarily for the passed block
diff --git a/activesupport/lib/active_support/core_ext/array/conversions.rb b/activesupport/lib/active_support/core_ext/array/conversions.rb
index 19220da2b1..e9e9cf445e 100644
--- a/activesupport/lib/active_support/core_ext/array/conversions.rb
+++ b/activesupport/lib/active_support/core_ext/array/conversions.rb
@@ -3,12 +3,20 @@ module ActiveSupport #:nodoc:
     module Array #:nodoc:
       # Enables to conversion of Arrays to human readable lists. ['one', 'two', 'three'] => "one, two, and three"
       module Conversions
-        # Converts the array to comma-seperated sentence where the last element is joined by the connector word (default is 'and').
-        def to_sentence(connector = 'and')
-          if length > 1
-            "#{self[0...-1].join(', ')}, #{connector} #{self[-1]}"
-          elsif length == 1
-            self[0]
+        # Converts the array to comma-seperated sentence where the last element is joined by the connector word. Options:
+        # * <tt>:connector</tt>: The word used to join the last element in arrays with more than two elements (default: "and")
+        # * <tt>:skip_last_comma</tt>: Set to true to return "a, b and c" instead of "a, b, and c".
+        def to_sentence(options = {})
+          options.assert_valid_keys(:connector, :skip_last_comma)
+          options.reverse_merge! :connector => 'and', :skip_last_comma => false
+          
+          case length
+            when 1
+              self[0]
+            when 2
+              "#{self[0]} #{options[:connector]} #{self[1]}"
+            else
+              "#{self[0...-1].join(', ')}#{options[:skip_last_comma] ? '' : ','} #{options[:connector]} #{self[-1]}"
           end
         end
 
diff --git a/activesupport/lib/active_support/core_ext/hash.rb b/activesupport/lib/active_support/core_ext/hash.rb
index e899d3e1e2..f16368b18b 100644
--- a/activesupport/lib/active_support/core_ext/hash.rb
+++ b/activesupport/lib/active_support/core_ext/hash.rb
@@ -1,7 +1,9 @@
 require File.dirname(__FILE__) + '/hash/keys'
 require File.dirname(__FILE__) + '/hash/indifferent_access'
+require File.dirname(__FILE__) + '/hash/reverse_merge'
 
 class Hash #:nodoc:
   include ActiveSupport::CoreExtensions::Hash::Keys
   include ActiveSupport::CoreExtensions::Hash::IndifferentAccess
+  include ActiveSupport::CoreExtensions::Hash::ReverseMerge
 end
diff --git a/activesupport/lib/active_support/core_ext/hash/reverse_merge.rb b/activesupport/lib/active_support/core_ext/hash/reverse_merge.rb
new file mode 100644
index 0000000000..46c53871d8
--- /dev/null
+++ b/activesupport/lib/active_support/core_ext/hash/reverse_merge.rb
@@ -0,0 +1,25 @@
+module ActiveSupport #:nodoc:
+  module CoreExtensions #:nodoc:
+    module Hash #:nodoc:
+      # Allows for reverse merging where its the keys in the calling hash that wins over those in the <tt>other_hash</tt>.
+      # This is particularly useful for initializing an incoming option hash with default values:
+      #
+      #   def setup(options = {})
+      #     options.reverse_merge! :size => 25, :velocity => 10
+      #   end
+      #
+      # The default :size and :velocity is only set if the +options+ passed in doesn't already have those keys set.
+      module ReverseMerge
+        def reverse_merge(other_hash)
+          other_hash.merge(self)
+        end
+
+        def reverse_merge!(other_hash)
+          replace(reverse_merge(other_hash))
+        end
+
+        alias_method :reverse_update, :reverse_merge
+      end
+    end
+  end
+end
+\ No newline at end of file
diff --git a/activesupport/test/core_ext/array_ext_test.rb b/activesupport/test/core_ext/array_ext_test.rb
index 2ee86c8af9..159dc2a478 100644
--- a/activesupport/test/core_ext/array_ext_test.rb
+++ b/activesupport/test/core_ext/array_ext_test.rb
@@ -19,7 +19,15 @@ class ArrayExtConversionTests < Test::Unit::TestCase
   end
   
   def test_to_sentence_with_connector
-    assert_equal "one, two, and also three", ['one', 'two', 'three'].to_sentence('and also')
+    assert_equal "one, two, and also three", ['one', 'two', 'three'].to_sentence(:connector => 'and also')
+  end
+  
+  def test_to_sentence_with_skip_last_comma
+    assert_equal "one, two and three", ['one', 'two', 'three'].to_sentence(:skip_last_comma => true)
+  end
+
+  def test_two_elements
+    assert_equal "one and two", ['one', 'two'].to_sentence
   end
   
   def test_one_element
diff --git a/activesupport/test/core_ext/hash_ext_test.rb b/activesupport/test/core_ext/hash_ext_test.rb
index f42b6fde2f..4ae2dd8e7c 100644
--- a/activesupport/test/core_ext/hash_ext_test.rb
+++ b/activesupport/test/core_ext/hash_ext_test.rb
@@ -118,4 +118,8 @@ class HashExtTest < Test::Unit::TestCase
     indiff = original.with_indifferent_access
     assert(!indiff.keys.any? {|k| k.kind_of? String}, "A key was converted to a string!")
   end
+
+  def test_reverse_merge
+    assert_equal({ :a => 1, :b => 2, :c => 10 }, { :a => 1, :b => 2 }.reverse_merge({:a => "x", :b => "y", :c => 10}) )
+  end
 end