add update-test

Library/Homebrew/cmd/update-test.rb

@@ -0,0 +1,26 @@
+require "extend/ENV"
+
+module Homebrew
+  def update_test
+    homebrew_repository_git = HOMEBREW_REPOSITORY/".git"
+
+    mktemp do
+      curdir = Pathname.new(Dir.pwd)
+
+      # copy Homebrew installation
+      cp_r homebrew_repository_git, curdir/".git"
+      safe_system "git", "checkout", "--force", "master"
+      safe_system "git", "reset", "--hard", "origin/master"
+
+      # Set git origin
+      safe_system "git", "config", "remote.origin.url", "file://#{homebrew_repository_git}"
+
+      # update ENV["PATH"]
+      ENV.extend(Stdenv)
+      ENV.prepend_path "PATH", "#{curdir}/bin"
+
+      # run brew update
+      safe_system "brew", "update"
+    end
+  end
+end