Replace issue templates with links to jenkins.io

[KalleOlaviNiemitalo]

Delete the issue templates from .github/ISSUE_TEMPLATE/ and instead add .github/ISSUE_TEMPLATE/config.yml to define links to JIRA at https://issues.jenkins.io/.

Your checklist for this pull request

• Make sure you are requesting to pull a topic/feature/bugfix branch (right side) and not your master branch!
  This PR is from my master branch because I want to demonstrate how GitHub reads the config from there.
• Ensure that the pull request title represents the desired changelog entry
• Please describe what you did
• Link to relevant issues in GitHub or in Jenkins JIRA
• Link to relevant pull requests, esp. upstream and downstream changes
• Did you provide a test-case? That demonstrates feature works or fixes the issue.
  You can try it out at https://github.com/KalleOlaviNiemitalo/bitbucket-branch-source-plugin/issues/new/choose.

[KalleOlaviNiemitalo]

https://github.com/jenkinsci/bitbucket-branch-source-plugin/issues/new/choose currently looks like this:

and https://github.com/KalleOlaviNiemitalo/bitbucket-branch-source-plugin/issues/new/choose looks like this:

So the differences are:

• Replaced the two "GitHub issue tracker has been dismissed" issue templates with a link to https://www.jenkins.io/participate/report-issue/redirect/#21428, which then offers Bug, Improvement, or Security Issue.
• Added a link "View open issues in JIRA" pointing to https://issues.jenkins.io/issues/?jql=resolution%20is%20EMPTY%20and%20component%3D21428. This is the same URL as in the "Open issues (Jira)" link at https://plugins.jenkins.io/cloudbees-bitbucket-branch-source.
• Added a link "Issue tracking policy" pointing to https://github.com/jenkinsci/bitbucket-branch-source-plugin/blob/master/README.md#issue-tracking-where-file-new-issues, because it's apparently not possible to have links within the "about" property.
• Removed "Blank issue", which would allow opening an issue in GitHub.
• "Report a security vulnerability" does not show up in my fork, although I did not explicitly remove it. I guess it's just because my fork is not in the jenkinsci organization so https://github.com/jenkinsci/.github/blob/master/SECURITY.md does not apply to it.

[nfalco79]

Do you remember that issue on github will be disabled on 1 Jun 2025?
Any files in the issue template folder will be deleted. I would suggest to not waste your time on this.

[KalleOlaviNiemitalo]

Disabling the GitHub issue tracker would break all links to previously filed issues. That is why I hope it will not be necessary.

Now that config.yml disables blank issues and there are no issue templates, https://github.com/jenkinsci/bitbucket-branch-source-plugin/issues/new/choose should redirect most users to Jira. However, it seems one can still open an issue in GitHub if one removes /choose from the URL. Perhaps using the GitHub command-line client too.