feature/build only branches with legacy asciidoc

[reakaleek]

Changes

Only build 8.x target branches.

Context

According to https://github.com/elastic/buildkite-pr-bot?tab=readme-ov-file#configuration-1 you can actually set the target_branch in pull-requests.org-wide.json.

However, the buildkite/docs-build-pr status check is usually a required check.

In this PR we exit early if the target branch doesn't match the pattern, so that the status check will still be green.

[github-actions]

A documentation preview will be available soon.

• 🔨 Buildkite builds
• 📚 HTML diff
• 📙 Preview page

Request a new doc build by commenting

• Rebuild this PR: run docs-build
• Rebuild this PR and all Elastic docs: run docs-build rebuild

_{run docs-build is much faster than run docs-build rebuild. A rebuild should only be needed in rare situations.}

_{If your PR continues to fail for an unknown reason, the doc build pipeline may be broken. Elastic employees can check the pipeline status here.}

[shainaraskas]

We have other docs sets that are not on stack versioning that wouldn't be caught in this fix. This would help a lot with certain repos but I wonder if it needs to be refactored to cover stuff like ECE 4+ and ECK 3+

[bmorelli25]

I'm trying to think through Shaina's comment. We could potentially pair Jan's change here with the repo-specific instructions that start on L68. We could write a script to parse conf.yaml and spit out a mapping of each repo and the versions of documentation that are contained within that repo. We could then check against those versions.

For example:

 # repositories with a docs dir and changelog
"apm-aws-lambda" | "apm-agent-android" | "apm-agent-nodejs" | "apm-agent-python" | "apm-agent-ruby" | "apm-agent-rum-js" | "apm-agent-go" | "apm-agent-java" | "apm-agent-dotnet" | "apm-agent-php" | "apm-agent-ios")
+ if ! [[ $GITHUB_PR_TARGET_BRANCH =~ {NEWREGEXHERE} ]]; then+ echo "Target branch '$GITHUB_PR_TARGET_BRANCH' is not a valid version branch (must be in format+ X.Y where X <= 8)"+ exit 0+ fi
git fetch origin "$GITHUB_PR_TARGET_BRANCH"
docs_diff=$(git diff --stat "origin/$GITHUB_PR_TARGET_BRANCH"...HEAD -- "./docs/**.asciidoc" CHANGELOG.asciidoc)
;;

(this is just to illustrate)