Use Github Webhook to auto-deploy when a merge to master is performed

[codeofmochi]

With webhooks, we can ask Github to push payloads to our server when a PR is merged to master: we could then automatically trigger the update script. Important considerations:

• A web server will need to listen to these hooks anyway. Should it be part of the express instance itself (probably not a good idea, in terms of security and stability)? Or do we create another server instance but we then also have to setup docker or systemd etc. ?
• Need to use a secret and secure the webhook server routes by verifying the secret hash sent by Github, see docs at https://docs.github.com/en/developers/webhooks-and-events/securing-your-webhooks

See docs at https://docs.github.com/en/developers/webhooks-and-events/webhooks

[s314cy]

The plan is to host a very simple Flask application running on some port, accessible at clic.epfl.ch/hooks/. The hook would trigger on pull requests (https://docs.github.com/en/developers/webhooks-and-events/webhooks/webhook-events-and-payloads#webhook-payload-object-34) with action set to closed and merged to true. Obviously, the secret token's SHA256 must be checked before calling the right update scripts.

[codeofmochi]

Sounds good, but what about using another Node / Express server? This would ensure language consistency across the ecosystem