Mirror from GitHub to gitlab.com and trigger pipeline

When I create a new repository on gitlab.com and enter a git URL from GitHub and select Mirror repository , the repository will only be synced once per hour and for some reason the pipeline doesn’t get triggered when the sync happens.

Can I trigger the sync over the REST API so that I can define a GitHub Webhook which will trigger it on every push.

And can I somehow tell gitlab.com to run the pipeline when a sync happens?

I could of course define another Webhook on Github to trigger it, but I wouldn’t be able to tell if the repos have synced yet. So I’d potentially trigger it too early.