Suddenly, cp_r works beautifully! This commit now lets us handle the

case where a directory is meant to be copied as a subdirectory to the
destination path when that path already exists. We also do the
appropriate error message when the dest path given is non-existent and
so is its parent.

Oh, crap, we should probably check that it's a directory that we are
merging into.

lib/fakefs.rb

@@ -24,7 +24,15 @@ module FakeFS
 
     def cp_r(src, dest)
       if dir = FileSystem.find(src)
-        FileSystem.add(dest, dir.entry.clone)
+        new_dir = FileSystem.find(dest)
+        if !new_dir
+          if !FileSystem.find(dest+'/../')
+            raise Errno::ENOENT, dest
+          end
+          FileSystem.add(dest, dir.entry.clone)
+        else
+          new_dir[dir.name] = dir.entry.clone
+        end
       else
         # This error sucks, but it conforms to the original Ruby
         # method.
@@ -170,7 +178,7 @@ module FakeFS
     end
 
     def clear
-      @dir_levels = []
+      @dir_levels = nil
       @fs = nil
     end
 

test/fakefs_test.rb

@@ -287,6 +287,26 @@ class FakeFSTest < Test::Unit::TestCase
     end
   end
 
+  def test_cp_r_handles_copying_directories
+    FileUtils.mkdir_p 'subdir'
+    Dir.chdir('subdir'){ File.open('foo', 'w'){|f| f.write 'footext' } }
+
+    FileUtils.mkdir_p 'baz'
+
+    # To a previously uncreated directory
+    FileUtils.cp_r('subdir', 'quux')
+    assert_equal 'footext', File.open('quux/foo'){|f| f.read }
+
+    # To a directory that already exists
+    FileUtils.cp_r('subdir', 'baz')
+    assert_equal 'footext', File.open('baz/subdir/foo'){|f| f.read }
+
+    # To a subdirectory of a directory that does not exist
+    assert_raises(Errno::ENOENT) {
+      FileUtils.cp_r('subdir', 'nope/something')
+    }
+  end
+
   def test_clone_clones_normal_files
     def here(fname); File.expand_path(File.dirname(__FILE__)+'/'+fname); end
     RealFile.open(here('foo'), 'w'){|f| f.write 'bar' }