I suspect the culprit of the crash is the GIT_AUTHOR_DATE. If I remove this before starting my script it works. I already pass expand_vars=False, but that isn't passed far enough down to make a differance.

My current workaround is to nulke the enviroment variables when invoking my script by using env -i <script> from the commit hook.

My ideal solution would be a flag to disable the copy of the os environ on git/cmd.py:699. This will not only eliminate this issue, but also any potential other interferance (think GIT_DIR and friends).

Replicate via:

export GIT_INDEX_FILE='.git/index'
export GIT_AUTHOR_DATE='@1574863356 +0100'
export GIT_EXEC_PATH='/usr/lib/git-core'
export GIT_AUTHOR_EMAIL='admin@dries007.net'
export GIT_PREFIX=''
export GIT_AUTHOR_NAME='Dries'

python3

import tempfile

import git


def main():
    with tempfile.TemporaryDirectory() as folder:
        repo = git.Repo.init(folder, expand_vars=False)
        repo.index.commit("Init test repo with empty commit.")
        repo.head.reference = repo.create_head("master")


if __name__ == "__main__":
    main()

Thanks,
Dries