Adding challenges through external repo fails

[CyrilleFranchet]

Hi,

I may be wrong but it's not possible to add a git repo with ctf challenge add {repo_url} at first. This command relies on git subtree which is a shell script. this script calls ensure_clean to check the HEAD reference but our repo is empty at this point.

I would add a git commit --allow-empty -m "Project created" after the git init in main.py.