diff -r 4481f1fd27b1 -r fb320398a21c mercurial/dirstate.py
--- a/mercurial/dirstate.py	Sat Jul 08 15:42:11 2017 -0700
+++ b/mercurial/dirstate.py	Sat Jul 08 16:18:04 2017 -0700
@@ -70,7 +70,7 @@
 
 class dirstate(object):
 
-    def __init__(self, opener, ui, root, validate):
+    def __init__(self, opener, ui, root, validate, sparsematchfn):
         '''Create a new dirstate object.
 
         opener is an open()-like callable that can be used to open the
@@ -80,6 +80,7 @@
         self._opener = opener
         self._validate = validate
         self._root = root
+        self._sparsematchfn = sparsematchfn
         # ntpath.join(root, '') of Python 2.7.9 does not add sep if root is
         # UNC path pointing to root share (issue4557)
         self._rootdir = pathutil.normasprefix(root)
@@ -197,6 +198,19 @@
             f[normcase(name)] = name
         return f
 
+    @property
+    def _sparsematcher(self):
+        """The matcher for the sparse checkout.
+
+        The working directory may not include every file from a manifest. The
+        matcher obtained by this property will match a path if it is to be
+        included in the working directory.
+        """
+        # TODO there is potential to cache this property. For now, the matcher
+        # is resolved on every access. (But the called function does use a
+        # cache to keep the lookup fast.)
+        return self._sparsematchfn()
+
     @repocache('branch')
     def _branch(self):
         try: