[JENKINS-60353] Enable PR-204 workaround all the time

[kshultzCB]

• JENKINS issue(s):
  • JENKINS-60353
  • JENKINS-54126
  • Possibly others.
• Description:
  • In short, this turns the workaround from PR-204 on all the time.
  • There will be a very small uptick in the number of API requests used with this change in place - but only in the event of getting a 40* response code back from GitHub
  • I don't expect this to solve all possible variants of the Jenkinsfile not found problem we've been battling for the last year and change. But some testing that @bitwiseman and I worked on together, in the context of JENKINS-60353, shows that this does at least solve that particular case. The case can be seen in github-api-plugin PR-665, which provides a simple test to simulate the issue.
  • It is still possible to disable the workaround, by setting the system property -Dorg.jenkinsci.plugins.github_branch_source.GitHubSCMProbe.JENKINS_54126_WORKAROUND=false.
• Documentation changes:
  • Probably no documentation needed, although mentioning this in a release note might be useful.
• Testing performed:
  • Existing unit tests all pass
  • Manual verification that running without this change produces the bug described in JENKINS-60353, while running with this change in place fixes the problem
• Users/aliases to notify:
  • @rsandell , who originally committed the workaround we're now enabling by default

[res0nance]

-Dorg.jenkinsci.plugins.github_branch_source.GitHubSCMProbe.JENKINS_54126_WORKAROUND=true

Disable should be setting it to false but the idea seems good. My instances have been plagued with this issue that seems impossible to replicate

[kshultzCB]

Good catch on that note. That was a copy/paste gone wrong, I’ve fixed it.

[bitwiseman]

This work around as whole will not be needed once we upgrade to a version of github-api that includes this: hub4j/github-api#665 .
I hope to get that included in the next week, just in case I'll go ahead and merge this now.