check: paginate by push date, not git commit date

[bmalehorn]

Context

github-pr-resource used to paginate by PushedDate. This is a timestamp GitHub stores on each commit at the time the user typed git push. By paginating by PushedDate, github-pr-resource would only trigger builds on PRs that have had a new commit pushed to them since the last time github-pr-resource ran. That makes sense.

In telia-oss#22 it was discovered that on pull requests created from forked branches have PushedDate: nil. To fix, the paginated on CommitDate, which is the time that the user types git commit.

However, this created telia-oss#26 - if someone types git commit, waits a few hours, then pushes, their commit won't be picked up because we've already handled newer commits.

I attempted to fix this in #4 by removing the filter entirely. This fixes the problem but increases the github token usage a lot.

Instead, fix this by applying https://github.com/mplzik/github-pr-resource/commit/edca4f5303b8086f6847012710398b9a26f1bdca and combining it with the PR creation date. This paginates by max(lastCommit.PushedDate || lastCommit.CommitDate, pullRequest.CreatedAt). In code, all of our commits have a PushedDate so we're back to the original, fixed behavior. It also handles the case where you push a branch, then don't open a pull request for several minutes.

This should reduce the github usage a lot, since we'll go from loading the data on all 300 open pull requests to only loading 1-5 pull requests that have opened since the last call.

Origin

Me

Summary of Changes

• hand-apply https://github.com/mplzik/github-pr-resource/commit/edca4f5303b8086f6847012710398b9a26f1bdca, which introduces an ChangedDate = PushedDate || CommitDate

Test Plan

• task test
• cat ~/tmp/test.json | go run cmd/check/main.go

{
  "source": {
    "repository": "opendoor-labs/code",
    "access_token": "ghp_<redacted>",
    "base_branch": "master"
  },
  "version": {
    "approved_review_count": "0",
    "changed": "2021-12-10T01:30:42Z",
    "commit": "0130ca9d1475adfc094a84b4b6c230122f97db4f",
    "committed": "2021-12-10T01:30:32Z",
    "pr": "38122",
    "state": "OPEN"
  }
}

I observed that this only returned the 4 new commits that have been updated since 2021-12-10T01:30:42Z.
To deploy:

• make docker image, push to admiral pipeline
  
• push docker image to code pipeline
• make 2 draft PRs to test it out

to deploy:

• make latest docker image

Documentation

N/A

[bmalehorn]

@dan-hipschman-od updated this to also take into account the pull request creation date.