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Automatic backporting workflow from 4.1 to 4.2 (#16271)
Motivation: We often backport PRs from 4.2 to 4.1. Because these branches are very similar, cherry-picking often applies cleanly. Modification: Add a workflow that triggers on PRs merged into 4.2 with the needs-cherry-pick-4.1 label, and tries to cherry-pick the merge commit onto 4.1 and create a pull-request. Finally, the workflow adds a comment to the original PR, linking the backport PR if the cherry-pick succeeded, or reporting failure if it didn't. The back port branch are pushed back to the netty/netty repository using the same SSH key we use to push release tags. The PRs and comments are created using a personal access token stored in a `PAT_TOKEN_READ_WRITE_PR` org secret. The PAT token must have "pull_request read/write" permission for it to work. Result: Easier to keep 4.1 up to date with bug fixes we do in 4.2. This PR attempts to fix the issues encountered with #16269
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‎.github/workflows/backport-41.yml‎

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name: Auto Backport to 4.1
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on:
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pull_request:
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types:
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- closed
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- labeled
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branches:
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- '4.2'
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jobs:
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backport:
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if: github.event.pull_request.merged && (
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github.event.action == 'closed' && contains(github.event.pull_request.labels.*.name, 'needs-cherry-pick-4.1') ||
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github.event.action == 'labeled' && contains(github.event.label.name, 'needs-cherry-pick-4.1'))
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runs-on: ubuntu-latest
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steps:
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- name: Checkout repository
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uses: actions/checkout@v6
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with:
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fetch-depth: '0' # Cherry-pick needs full history
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token: '${{ secrets.GITHUB_TOKEN }}'
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- name: Setup git configuration
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run: |
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git config --global user.email "netty-project-bot@users.noreply.github.com"
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git config --global user.name "Netty Project Bot"
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- name: Install SSH key
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uses: shimataro/ssh-key-action@v2
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with:
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key: ${{ secrets.SSH_PRIVATE_KEY_PEM }}
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known_hosts: ${{ secrets.SSH_KNOWN_HOSTS }}
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- name: Create backport PR branch and cherry-pick
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id: cherry-pick
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run: |
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MERGE_COMMIT="${{ github.event.pull_request.merge_commit_sha }}"
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echo "Backporting commit: $MERGE_COMMIT"
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BACKPORT_BRANCH="backport-pr-${{ github.event.pull_request.number }}-to-4.1"
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git fetch origin 4.1:4.1
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git checkout -b "$BACKPORT_BRANCH" 4.1
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if git cherry-pick -x "$MERGE_COMMIT"; then
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echo "Cherry-pick successful"
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echo "success=true" >> "$GITHUB_OUTPUT"
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else
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echo "Cherry-pick failed - conflicts detected"
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echo "success=false" >> "$GITHUB_OUTPUT"
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git cherry-pick --abort
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exit 1
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fi
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echo "branch=$BACKPORT_BRANCH" >> "$GITHUB_OUTPUT"
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- name: Push backport branch
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id: push
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if: steps.cherry-pick.outputs.success == 'true'
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run: |
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if ! git push origin "${{ steps.cherry-pick.outputs.branch }}"; then
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echo "Backport branch push failed"
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echo "push_failed=true" >> "$GITHUB_OUTPUT"
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exit 1
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fi
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- name: Create pull request
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if: steps.cherry-pick.outputs.success == 'true'
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uses: actions/github-script@v8
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with:
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github-token: '${{ secrets.PAT_TOKEN_READ_WRITE_PR }}'
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script: |
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const { data: pr } = await github.rest.pulls.create({
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owner: context.repo.owner,
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repo: context.repo.repo,
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title: `Backport 4.1: ${context.payload.pull_request.title}`,
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head: '${{ steps.cherry-pick.outputs.branch }}',
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base: '4.1',
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body: `Backport of #${context.payload.pull_request.number} to 4.1\n` +
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`Cherry-picked commit: ${context.payload.pull_request.merge_commit_sha}\n\n---\n` +
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`${context.payload.pull_request.body || ''}`
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});
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console.log(`Created backport PR: ${pr.html_url}`);
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await github.rest.issues.createComment({
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owner: context.repo.owner,
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repo: context.repo.repo,
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issue_number: context.payload.pull_request.number,
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body: `Backport PR for 4.1: #${pr.number}`
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});
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- name: Report cherry-pick conflicts
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if: failure() && steps.cherry-pick.outputs.success == 'false'
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uses: actions/github-script@v8
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with:
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github-token: '${{ secrets.PAT_TOKEN_READ_WRITE_PR }}'
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script: |
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await github.rest.issues.createComment({
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owner: context.repo.owner,
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repo: context.repo.repo,
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issue_number: context.payload.pull_request.number,
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body: `Could not create automatic backport PR.\nGot conflicts when cherry-picking onto 4.1.`
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});
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- name: Report backport branch push failure
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if: failure() && steps.push.outputs.push_failed == 'true'
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uses: actions/github-script@v8
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with:
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github-token: '${{ secrets.PAT_TOKEN_READ_WRITE_PR }}'
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script: |
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await github.rest.issues.createComment({
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owner: context.repo.owner,
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repo: context.repo.repo,
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issue_number: context.payload.pull_request.number,
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body: `Could not create automatic backport PR.\n`+
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`I could cherry-pick onto 4.1 just fine, but pushing the new branch failed.`
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});

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