def wrapdirstate(repo, dirstate):

    def _editfunc(fn):

        def _wrapper(self, *args):

            return fn(self, *args)

        return _wrapper

    class narrowdirstate(dirstate.__class__):

        def walk(self, match, subrepos, unknown, ignored, full=True,

                 narrowonly=True):

            if narrowonly:

                # hack to not exclude explicitly-specified paths so that they

                # can be warned later on e.g. dirstate.add()

                em = matchmod.exact(match._root, match._cwd, match.files())

                nm = matchmod.unionmatcher([repo.narrowmatch(), em])

                match = matchmod.intersectmatchers(match, nm)

            return super(narrowdirstate, self).walk(match, subrepos, unknown,

                                                    ignored, full)

        # Prevent adding/editing/copying/deleting files that are outside the

        # sparse checkout

        @_editfunc

        def normal(self, *args):

            return super(narrowdirstate, self).normal(*args)

        @_editfunc

        def add(self, *args):

            return super(narrowdirstate, self).add(*args)

        @_editfunc

        def normallookup(self, *args):

            return super(narrowdirstate, self).normallookup(*args)

        @_editfunc

        def copy(self, *args):

            return super(narrowdirstate, self).copy(*args)

        @_editfunc

        def remove(self, *args):

            return super(narrowdirstate, self).remove(*args)

        @_editfunc

        def merge(self, *args):

            return super(narrowdirstate, self).merge(*args)

        def rebuild(self, parent, allfiles, changedfiles=None):

            if changedfiles is None:

                # Rebuilding entire dirstate, let's filter allfiles to match the

                # narrowspec.

                allfiles = [f for f in allfiles if repo.narrowmatch()(f)]

            super(narrowdirstate, self).rebuild(parent, allfiles, changedfiles)

        def restorebackup(self, tr, backupname):

            self._opener.rename(_narrowbackupname(backupname),

                                narrowspec.FILENAME, checkambig=True)

            super(narrowdirstate, self).restorebackup(tr, backupname)

        def savebackup(self, tr, backupname):

            super(narrowdirstate, self).savebackup(tr, backupname)

            narrowbackupname = _narrowbackupname(backupname)

            self._opener.tryunlink(narrowbackupname)

            hgutil.copyfile(self._opener.join(narrowspec.FILENAME),

                            self._opener.join(narrowbackupname), hardlink=True)

        def clearbackup(self, tr, backupname):

            super(narrowdirstate, self).clearbackup(tr, backupname)

            self._opener.unlink(_narrowbackupname(backupname))

    dirstate.__class__ = narrowdirstate

    return dirstate