Add 'unload'

Library/Homebrew/cmd/versions.rb

@@ -87,7 +87,7 @@ class Formula
 
         # Unload the class so Formula#version returns the correct value
         begin
-          Object.send(:remove_const, Formula.class_s(name))
+          Formulary.unload_formula name
           nostdout { Formula.factory(path).version }
         rescue *IGNORED_EXCEPTIONS => e
           # We rescue these so that we can skip bad versions and

Library/Homebrew/formulary.rb

@@ -1,6 +1,10 @@
 # The Formulary is responsible for creating instances of Formula.
 class Formulary
 
+  def self.unload_formula formula_name
+    Object.send(:remove_const, Formula.class_s(formula_name))
+  end
+
   def self.formula_class_defined? formula_name
     Object.const_defined?(Formula.class_s(formula_name))
   end