Issues when using shunt alongside Woodpecker CI tests

[sebaseg-dev]

Hi @rbtr 👋

We encountered some troubles when testing merge queue integration into Codeberg with shunt on our tests repo.

We implemented our own Woodpecker CI instance and connected to our organisation and repos on Codeberg. We have some issues when trying to make it run alongside shunt. In the Codeberg's UI, it appears that merge queue is ran and finished before other Woodpecker's checks termination (see the screenshot below).

In other cases, we had to reboot shunt instance (for example if Woodpecker checks fail, PR is not merged, then if we commit changes to make tests pass, shunt had to be rebooted to take into account this PR in the merge queue).

Thank you !

[rbtr]

Sounds related to #73. It should not let a PR enter the merge queue until it would normally be mergeable (excluding its own merge-queue check). Let me add a test scenario for this and try and fix.