allow for {p,q} literals in globs

lib/fakefs/file_system.rb

@@ -121,7 +121,10 @@ module FakeFS
           directories_under(dir)
         end
       else
-        dir.reject {|k,v| /\A#{pattern.gsub('?','.').gsub('*', '.*')}\Z/ !~ k }.values
+        pattern = pattern.gsub('?','.').gsub('*', '.*')
+        pattern = pattern.gsub(%r{\{([^\}]+)\}}) { |all| "(#{$1.gsub(',', '|')})" }
+
+        dir.reject {|k,v| /\A#{pattern}\Z/ !~ k }.values
       end
 
       if parts.empty? # we're done recursing

test/fakefs_test.rb

@@ -569,6 +569,8 @@ class FakeFSTest < Test::Unit::TestCase
 
     assert_equal ['/path/bar/baz'], Dir['/path/bar/**/*']
 
+    assert_equal ['/path/bar', '/path/foo'], Dir['/path/{foo,bar}'].sort
+
     FileUtils.cp_r '/path', '/otherpath'
 
     assert_equal %w( /otherpath/foo /otherpath/foobar /path/foo /path/foobar ), Dir['/*/foo*']