[MERGE] Support status for nested trees

[Ian Clatworthy]

Aaron Bentley wrote:

> This patch implements status support for nested trees.  It builds on my
> previous CompositeTree patch.

bb:tweak

> +    def test_subtree_status(self):
> +        tree = self.make_branch_and_tree('.', format='dirstate-with-subtree')
> +        subtree = self.make_branch_and_tree('subtree',
> +                                            format='dirstate-with-subtree')
> +        self.build_tree(['file1', 'subtree/file2'])
> +        tree.add_reference(subtree)

Each of the remaining tests start with these same 4 lines so put them
out into a helper method please.

> +    def test_subtree_status_specific(self):
> +        """test specifi status with unversioned files"""

Please rename with a _unversioned appended to the name.
s/specifi/specific/.

> +    def test_subtree_status_specific2(self):
> +        """test status with specific versioned files"""

Please s/specific2/specific_versioned/.

Ian C.