def _history(self, path, start, end, pool):
        path_utf8 = _to_svn(pool(), self.scope, path)
        if start < end:
            start, end = end, start
        if (start, end) == (1, 0): # only happens for empty repos
            return
        root = fs.revision_root(self.fs_ptr, start, pool())
        # fs.node_history leaks when path doesn't exist (#6588)
        if fs.check_path(root, path_utf8, pool()) == core.svn_node_none:
            return
        tmp1 = Pool(pool)
        tmp2 = Pool(pool)
        history_ptr = fs.node_history(root, path_utf8, tmp1())
        cross_copies = 1
        while history_ptr:
            history_ptr = fs.history_prev(history_ptr, cross_copies, tmp2())
            tmp1.clear()
            tmp1, tmp2 = tmp2, tmp1
            if history_ptr:
                path_utf8, rev = fs.history_location(history_ptr, tmp2())
                tmp2.clear()
                if rev < end:
                    break
                path = _from_svn(path_utf8)
                yield path, rev
        del tmp1
        del tmp2
`path` is a unicode path in the scope.
dataset/ETHPy150Open edgewall/trac/tracopt/versioncontrol/svn/svn_fs.py/SubversionRepository._history