Find root of repo that contains the actual script

This makes it possible to run the render script from anywhere and have
it still function correctly.

tools/render

@@ -5,13 +5,14 @@
 import functools
 import json
 import pathlib
+import sys
 
 import git
 import requests
 import yaml
 from jinja2 import Environment, FileSystemLoader, StrictUndefined, Template
 
-REPO = git.Repo(".", search_parent_directories=True)
+REPO = git.Repo(sys.path[0], search_parent_directories=True)
 assert REPO.working_dir is not None
 
 ROOT = pathlib.Path(REPO.working_dir)