Support cancelling merged pull requests

[potiuk]

It would be great to add an option for cancelling pull request actions for already merged pull requests.

It happens sometimes that you can decide to merge a PR without waiting for the action to complete. Actions for such merged PRs can be safely cancelled.

[potiuk]

cc: @TobKed @mik-laj @kaxil @ashb -> yet another optimization we can add to the cancel action (And use in Airflow).

PRs are most welcome :) - I have other stuff to do in the next few days and might not be able to implement it quickly.

[kaxil]

I assumed they get cancelled 🤔 but may be not!

[ashb]

I'm working on self hosted runners, so won't get to it this week

[potiuk]

No - they are not. There is no mechanism for that. I often cancel them manually :(

[kaxil]

No - they are not. There is no mechanism for that. I often cancel them manually :(

Yea -- If some jobs have not started yet -- then because the checkout action fails since there is no Branch (again assuming that branch is deleted) it gets cancelled.

But the ones that have started will keep on running -- so yeah good call.