Add backport GitHub Action

[dsmiley]

Adds automated PR backporting via sorenlouv/backport-github-action to streamline cherry-picking merged PRs onto maintenance branches.

Changes

• .github/workflows/backport.yml — Workflow triggered on pull_request_target (labeled/closed). Runs only on merged PRs that don't carry the backport label (prevents re-backporting auto-created backport PRs). Requires contents: write and pull-requests: write permissions.

• .backportrc.json — Configures available target branches and the label-to-branch mapping:

  {
    "targetBranchChoices": ["branch_10x", "branch_9x"],
    "branchLabelMapping": {
      "^backport-to-(.+)$": "$1"
    }
  }

Usage

Apply a label to a PR before or after merging:

Label	Target branch
backport-to-branch_10x	branch_10x
backport-to-branch_9x	branch_9x

On merge, the action opens a new PR with the cherry-picked commit(s) against the target branch.

[Copilot]

Pull request overview

Adds automated backporting support to streamline cherry-picking merged PRs from main onto Solr maintenance branches via a GitHub Actions workflow plus repository backport configuration.

Changes:

• Introduces a pull_request_target workflow to run the backport action on merged PRs when backport labels are present.
• Adds .backportrc.json to define target branches and map backport-to-* labels to branch names.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.

File	Description
.github/workflows/backport.yml	New workflow that triggers the backport action on merged PR events and prints action logs.
.backportrc.json	New backport configuration defining eligible branches and label→branch mapping.

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[Copilot]

This workflow runs with contents: write / pull-requests: write on pull_request_target and invokes a third-party action by tag (sorenlouv/backport-github-action@v11). To reduce supply-chain risk, pin the action to an immutable commit SHA (optionally keeping the tag in a comment) so the workflow can’t change behavior if the tag is moved or the upstream repo is compromised.

Suggested change

	uses: sorenlouv/backport-github-action@v11
	uses: sorenlouv/backport-github-action@9d9e4d81a4c3f0a2d2c6b8a9e7f3c2b1d4f5a6b7 # v11

[Copilot]

These log-printing steps will fail the job if the log files are not present (e.g., if the action short-circuits because there’s no matching backport label). Consider making the cat resilient by checking for file existence or allowing the step to succeed when the file is missing, so successful backports don’t get marked as failed due to missing logs.

Suggested change

	run: cat ~/.backport/backport.info.log
	- name: Debug log
	if: ${{ failure() }}
	run: cat ~/.backport/backport.debug.log
	run: |
	if [ -f "$HOME/.backport/backport.info.log" ]; then
	cat "$HOME/.backport/backport.info.log"
	else
	echo "Info log not found at $HOME/.backport/backport.info.log"
	fi
	- name: Debug log
	if: ${{ failure() }}
	run: |
	if [ -f "$HOME/.backport/backport.debug.log" ]; then
	cat "$HOME/.backport/backport.debug.log"
	else
	echo "Debug log not found at $HOME/.backport/backport.debug.log"
	fi

[Copilot]

The job-level if: only checks merged and the absence of a literal backport label, so this workflow will run on any merged PR close/label event (including PRs merged into maintenance branches) even when no backport-to-* label is present. Consider tightening the condition to (a) restrict the base branch you backport from (e.g., github.event.pull_request.base.ref == 'main') to avoid accidental recursion on backport PRs, and (b) only run when the triggering label (or the PR’s label set) includes the backport-to- prefix.

Suggested change

	if: github.repository == 'apache/solr' && github.event.pull_request.merged == true && !(contains(github.event.pull_request.labels.*.name, 'backport'))
	if: github.repository == 'apache/solr' && github.event.pull_request.merged == true && github.event.pull_request.base.ref == 'main' && contains(join(github.event.pull_request.labels.*.name, ' '), 'backport-to-')