[JENKINS-64800] Recursively check previous builds for changes during polling

[stuartrowe]

Fix for https://issues.jenkins.io/browse/JENKINS-64800.

My team recently ran into this issue because of problems with authentication against our company's LDAP servers.

In our case a run would fail at the p4 checkout stage because of the authentication issues. Subsequent polling tasks for the job would fail to find new changes because the last run didn't have an associated TagAction.

As suggested in one of the comments on JENKINS-64800, our fix iterates through earlier builds in an attempt to find a baseline for polling.

Testing done

There aren't currently any unit tests related to polling. Instead my team created a manual test with the following steps:

1. Temporarily swap a valid credential with an invalid one
2. Run a job using that credential and note that it fails during checkout
3. Restore the valid credential
4. Submit a change to trigger polling and confirm that polling is successful

We confirmed that this test failed with p4-plugin 1.14.1 and succeeded with the fix.

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[stuartrowe]

@p4paul could you please review this when you have a chance?

[stuartrowe]

Close + Reopen to re-trigger CI.

[stuartrowe]

@p4paul @skumar7322 are either of you available to review this?

[skumar7322]

Thanks, @stuartrowe for initiating this pull request. This change will throw the NPE when lastRun is null. Because of this, there are test failures in PollingTest, PerforceSCMSourceTest suit.
Please execute these test suites for your proposed changes. Also given our planned workload, we intend to address JENKINS-64800 in our upcoming releases.

[stuartrowe]

@skumar7322 thanks for pointing that out, I had overlooked it somehow. Should be addressed now 🤞.

[stuartrowe]

@skumar7322 there seems to be an issue with org.jenkinsci.plugins.p4.SimpleTestServer that is affecting other PRs too.

[stuartrowe]

@skumar7322 is there any update on the next planned release and a fix for JENKINS-64800? If not, can this PR please be revisited?

[skumar7322]

Hi @stuartrowe this change looks good to me. I will run the tests on this and merge it once all is good.