Pass change_parent_directories param when instantiating git.Repo.

[laur89]

Otherwise git-playback works only if your working dir is on the repo root.

Note that git/repo/base.py's Repo constructor is

    def __init__(self, path=None, odbt=DefaultDBType, search_parent_directories=False):

meaning we need to pass the dbtype as well.
And in the same file DefaultDBType is defined as

DefaultDBType = GitDB

(with GitDB import as:)

from git.db import (
    GitCmdObjectDB,
    GitDB
)