Poll to make sure PR checks are finished before giving up in isPullRequestMergeable

[roryabraham]

Problem

We've seen a few workflows like this where a PR enters mergeable_state === 'blocked', and isPullRequestMergeable gives up and determines that there's a problem and the PR can't be merged. Only moments later, the PR becomes mergeable.

I believe this is a race condition, because the verifySignedCommits PR check is running, and while the PR checks are ongoing the PR is in mergeable_state === 'blocked'. Sometimes verifySignedCommits finishes in less that 10 seconds and so the polling mechanism doesn't recheck the PR until it's done.

Solution

Poll the PR checks and make sure they're done before giving up due to mergeable_state === 'blocked'.