SOLR-17619 Fix the regex used to detect Github Pull request in branch name

[janhoy]

https://issues.apache.org/jira/browse/SOLR-17619

Context: Running ./gradlew newChangelog generates a logchange yaml based on git branch name.

The old regex matched any number in the branch name, so SOLR-1234-New feature would add issue: 1234 to the changelog yaml, misinterpreting it as a github issue number. Reason was the extra ? after the parenthesis which makes it optional. The new regex matches strictly one of

• PR-123
• GH-123
• GITHUB-123
• #123

These will also match due to the #123 part, not the prefix

• PR#123
• GH#123
• GITHUB#123

[hossman]

i don't know a lot about what kinds of naming conventions github users use when naming branches but i wonder if -- instead of requiring the (PR-|GH-|GITHUB-|#) prefix in the branch name to mean "subsequent digits are a github PR#" -- it might make sense to do something like this...

    def githubMatcher = gitBranch =~ /(PR-|GH-|GITHUB-|#)(\d+)/
    def githubRef = (githubMatcher && ! jiraMatcher) ? githubMatcher.group(2) : ""
    def githubLink = (githubMatcher && ! jiraMatcher) ? "issues:\n  - ${githubRef}" : ""

...ie:

• if we've already determined the branch name has a SOLR-XXX jira component, then don't bother checking for a github PR# component (at all)
• if it does not have a SOLR-XXX jira component, then any number in the branch name might be a github PR#

would that make more sense?
Is anyone out there naming branches SOLR-1235-fix-stuff-in-PR-678 ?

[janhoy]

Since this is from branch name, we can probably skip PR detection, for two reasons:

1. # is prob an illegal char in branch
2. You create the branch before you know what Pr…