Merge rubygems master.

This is RC version of Rubygems 2.7.0.
  688fb7e83c

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@60133 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

lib/rubygems/util.rb

@@ -109,26 +109,15 @@ module Gem::Util
   ##
   # Enumerates the parents of +directory+.
 
-  def self.traverse_parents directory
+  def self.traverse_parents directory, &block
     return enum_for __method__, directory unless block_given?
 
     here = File.expand_path directory
-    start = here
-
-    Dir.chdir start
-
-    begin
-      loop do
-        yield here
-
-        Dir.chdir '..'
-
-        return if Dir.pwd == here # toplevel
-
-        here = Dir.pwd
-      end
-    ensure
-      Dir.chdir start
+    loop do
+      Dir.chdir here, &block
+      new_here = File.expand_path('..', here)
+      return if new_here == here # toplevel
+      here = new_here
     end
   end