Correctly obtain git.cmd.Git

See https://gitpython.readthedocs.io/en/stable/reference.html#git.cmd.Git

Using a `Repo` is not the correct argument to initialize the class. However GitPython is too lazy to raise an exception and just silently treats it as None, see  https://github.com/gitpython-developers/GitPython/blob/146202cdcbed8239651ccc62d36a8e5af3ceff8c/git/cmd.py#L584 https://github.com/gitpython-developers/GitPython/blob/146202cdcbed8239651ccc62d36a8e5af3ceff8c/git/util.py#L403

biothings/utils/version.py

@@ -249,7 +249,7 @@ def get_source_code_info(src_file):
         logging.exception("Can't find a github repository for file '%s'" % src_file)
         return None
     try:
-        gcmd = Git(repo)
+        gcmd = repo.git
         hash = gcmd.rev_list(-1, repo.active_branch, abs_src_file)
         rel_src_file = abs_src_file.replace(repo.working_dir, "").strip("/")
         if not hash: