deps: remove need for Array extension

Library/Homebrew/cmd/deps.rb

@@ -11,14 +11,18 @@ module Homebrew extend self
       puts_deps_tree ARGV.formulae
     else
       raise FormulaUnspecifiedError if ARGV.named.empty?
-      all_deps = ARGV.formulae.map do |f|
-        ARGV.one? ? f.deps.default : f.recursive_dependencies
-      end.intersection.map(&:name)
+      all_deps = deps_for_formulae ARGV.formulae
       all_deps.sort! unless ARGV.include? "-n"
       puts all_deps
     end
   end
 
+  def deps_for_formulae(formulae)
+    formulae.map do |f|
+      ARGV.one? ? f.deps.default : f.recursive_dependencies
+    end.inject(&:&).map(&:name)
+  end
+
   def puts_deps(formulae)
     formulae.each { |f| puts "#{f.name}: #{f.deps*' '}" }
   end
@@ -38,12 +42,3 @@ module Homebrew extend self
     end
   end
 end
-
-class Array
-  def intersection
-    a = []
-    each{ |b| a |= b }
-    each{ |c| a &= c }
-    a
-  end
-end