[Chore]: Investigate why the github-pr-resource is occasionally skipping versions

[georgethebeatle]

Background

We are leveraging the github-pr-resource to trigger the e2e tests on Concourse for every PR that comes in. For security reasons we are only running PRs that have the e2e-allowed label set on them. The allow-e2e task, which also watches PRs via the pr resource makes sure the test run is auto-approved if the commiter is a team member or one of our bots. Sadly, sometimes this resource skips some PRs, especially when there are many newly open PRs, like when dependabot does a few bumps. In such cases we need to manually allow e2e execution and potentially rebase or force push the change in order to trigger the tests. This is annoying and slows us down.

Action to take

Look at the github-pr-resource source code and attempt to fix the problem

Impact

Smooth PR flow

Dev Notes

No response

[danail-branekov]

See telia-oss/github-pr-resource#26

Apparently this is an old issue that can occur when rebasing PR branches. The root cause seems to be that the check step of the resource is checking the CommitDate, rather than the PushDate of a commit. When a branch is rebased, the CommitDate of a commit do not change, therefore the resource thinks that it is an old one.

The resource used to be checking the PushDate but it turned out that the field is nil for PRs coming from forks. Switching to checking for CommitDate seems to be the way they addressed it.

The obvious solution of this is to check PushDate, if nil, fallback to CommitDate. This has been already suggested but it did not get much of an attention. There are multiple PRs opened to address the issue, but none of them has been actually merged.

However, there are forks of the project and one of them seem to be containing a fix we need: opendoor-labs/github-pr-resource#6

So what can we do:

• Create yet another fork where we cherrypick a fix (or even fix it ourselves if we believe we can do that better)
• Switch to someone else's fork and hope that they maintain it
• Try pushing for fixing the issue (I doubt we could get much attention from the maintainers - the issue is almost 5 years old, multiple fixes/PRs have been proposed, none was actually merged)

[danail-branekov]

This commit's message also provides some explanation: ctreatma/github-pr-resource@c9ee589

On standup today we discussed that we need to make sure that the issue above is the culprit.

We should probably wait for the issue to occur and try debugging the check step of the resource to figure out why such PRs remain unnoticed.

blocking until the issue appears again

[kieron-dev]

We've decided to cherry-pick telia-oss/github-pr-resource#205 into eirini-forks. We agree with the argument that the date filtering is wrong and causes skips. We don't care about extra versions returned that concourse will filter out anyway. So it looks like a simple fix that we can maintain if upstream ever moves again.

So let's see how this goes...