Overwrite subfolders' state when setting states in folder dialog

Fixes #248

hscommon/path.py

@@ -117,6 +117,17 @@ class Path(tuple):
         first = self[0]
         return (len(first) == 2) and (first[1] == ':')
     
+    def is_parent_of(self, other):
+        """Whether ``other`` is a subpath of ``self``.
+
+        Almost the same as ``other in self``, but it's a bit more self-explicative and when
+        ``other == self``, returns False.
+        """
+        if other == self:
+            return False
+        else:
+            return other in self
+
     def remove_drive_letter(self):
         if self.has_drive_letter():
             return self[1:]

hscommon/tests/path_test.py

@@ -163,6 +163,11 @@ def test_contains(force_ossep):
     assert 'bleh' not in p
     assert Path('foo') not in p
 
+def test_is_parent_of(force_ossep):
+    assert Path(('foo','bar')).is_parent_of(Path(('foo','bar','bleh')))
+    assert not Path(('foo','bar')).is_parent_of(Path(('foo','baz')))
+    assert not Path(('foo','bar')).is_parent_of(Path(('foo','bar')))
+
 def test_windows_drive_letter(force_ossep):
     p = Path(('c:',))
     eq_('c:\\',str(p))