added support for recursive globbing

FakeDir.glob now handles recursive globs (i.e. '**') like the standard
lib Dir.  Previously they were treated identically to single wild cards
(i.e. '*')

Resolves issue #16
http://github.com/defunkt/fakefs/issues#issue/16

lib/fakefs/file_system.rb

@@ -106,13 +106,31 @@ def find_recurser(dir, parts)
       return [] unless dir.respond_to? :[]
 
       pattern , *parts = parts
-      matches = dir.reject {|k,v| /\A#{pattern.gsub('?','.').gsub('*', '.*')}\Z/ !~ k }.values
+      matches = case pattern
+      when '**'
+        case parts
+        when ['*'], []
+          parts = [] # end recursion
+          directories_under(dir).map do |d|
+            d.values.select{|f| f.is_a? FakeFile }
+          end.flatten.uniq
+        else
+          directories_under(dir)
+        end
+      else
+        dir.reject {|k,v| /\A#{pattern.gsub('?','.').gsub('*', '.*')}\Z/ !~ k }.values
+      end
 
       if parts.empty? # we're done recursing
         matches
       else
         matches.map{|entry| find_recurser(entry, parts) }
       end
     end
+
+    def directories_under(dir)
+      children = dir.values.select{|f| f.is_a? FakeDir}
+      ([dir] + children + children.map{|c| directories_under(c)}).flatten.uniq
+    end
   end
 end

test/fakefs_test.rb

@@ -397,6 +397,21 @@ def test_dir_glob_handles_root
     #assert_equal ['/'], Dir['/']
   end
 
+  def test_dir_glob_handles_recursive_globs
+    File.open('/one/two/three/four.rb', 'w')
+    File.open('/one/five.rb', 'w')
+    assert_equal ['/one/five.rb', '/one/two/three/four.rb'], Dir['/one/**/*.rb']
+    assert_equal ['/one/two'], Dir['/one/**/two']
+    assert_equal ['/one/two/three'], Dir['/one/**/three']
+  end
+
+  def test_dir_recursive_glob_ending_in_wildcards_only_returns_files
+    File.open('/one/two/three/four.rb', 'w')
+    File.open('/one/five.rb', 'w')
+    assert_equal ['/one/five.rb', '/one/two/three/four.rb'], Dir['/one/**/*']
+    assert_equal ['/one/five.rb', '/one/two/three/four.rb'], Dir['/one/**']
+  end
+
   def test_chdir_changes_directories_like_a_boss
     # I know memes!
     FileUtils.mkdir_p '/path'