Optional start_day argument for Time#all_week.

Closes #4883

activesupport/lib/active_support/core_ext/time/calculations.rb

@@ -273,9 +273,9 @@ def all_day
     beginning_of_day..end_of_day
   end
 
-  # Returns a Range representing the whole week of the current time.
-  def all_week
-    beginning_of_week..end_of_week
+  # Returns a Range representing the whole week of the current time. Week starts on start_day (default is :monday, i.e. end of Sunday).
+  def all_week(start_day = :monday)
+    beginning_of_week(start_day)..end_of_week(start_day)
   end
 
   # Returns a Range representing the whole month of the current time.

activesupport/test/core_ext/time_ext_test.rb

@@ -807,6 +807,7 @@ def test_all_day
 
   def test_all_week
     assert_equal Time.local(2011,6,6,0,0,0)..Time.local(2011,6,12,23,59,59,999999.999), Time.local(2011,6,7,10,10,10).all_week
+    assert_equal Time.local(2011,6,5,0,0,0)..Time.local(2011,6,11,23,59,59,999999.999), Time.local(2011,6,7,10,10,10).all_week(:sunday)
   end
 
   def test_all_month