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Handle issues:labeled trigger for cherry-pick on already-merged PRs #71

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Handle issues:labeled trigger for cherry-pick on already-merged PRs #71

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3638cfb
Add shared cherry-pick engine and cross-repo gatekeeper workflows
bunnam988 Aug 7, 2026
2c430dd
Fix cherry-pick and gatekeeper workflows for prod
bunnam988 Aug 7, 2026
36d4de5
Handle issues:labeled trigger for already-merged PR cherry-picks
bunnam988 Aug 7, 2026
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257 changes: 257 additions & 0 deletions .github/workflows/cherry-pick.yml
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name: Shared Cherry-Pick Engine

on:
workflow_call:
inputs:
raw_labels:
description: 'JSON array of labels from the triggering PR event'
required: true
type: string
trigger_label:
description: 'The specific label that triggered this event (from github.event.label.name). Empty for closed events.'
required: false
type: string
default: ''
pr_number_override:
description: 'PR number when triggered via issues:labeled on an already-merged PR (github.event.pull_request context is unavailable in that case).'
required: false
type: string
default: ''
secrets:
CROSS_REPO_TOKEN:
description: 'PAT with org-wide repo write access for cross-repo label propagation'
required: false

jobs:
backport:
runs-on: ubuntu-latest
steps:
- name: Extract Metadata & Propagate to Sister PRs
id: parse_meta
env:
GH_TOKEN: ${{ secrets.CROSS_REPO_TOKEN || secrets.GITHUB_TOKEN }}
# For issues:labeled events on merged PRs, pull_request context is empty — construct URL from override
CURRENT_PR_URL: ${{ inputs.pr_number_override != '' && format('https://github.com/{0}/pull/{1}', github.repository, inputs.pr_number_override) || github.event.pull_request.html_url }}
EVENT_LABEL: ${{ github.event.label.name }}
run: |
# 1. Parse the target destination branch(es) and custom topic label
# Prefer the event label (the label that was just added) over grepping the full list
TRIGGER_LABEL="${{ inputs.trigger_label }}"
# If caller didn't pass trigger_label, try from event context directly
if [ -z "$TRIGGER_LABEL" ]; then
TRIGGER_LABEL="$EVENT_LABEL"
fi

if [[ "$TRIGGER_LABEL" == cherry-pick\ to\ * ]]; then
# Single target from labeled event
TARGET_BRANCHES="${TRIGGER_LABEL#cherry-pick to }"
else
# Fallback for 'closed' events: process ALL cherry-pick labels (handles pre-merge labeling)
TARGET_BRANCHES=$(echo '${{ inputs.raw_labels }}' | jq -r '.[] | .name' | grep "cherry-pick to " | sed 's/cherry-pick to //' || true)
fi

CUSTOM_TOPIC=$(echo '${{ inputs.raw_labels }}' | jq -r '.[] | .name' | grep "^topic:" | head -n 1)

if [ -z "$TARGET_BRANCHES" ]; then
echo "No valid cherry-pick destination branch found. Exiting."
exit 0
fi

# Output as newline-separated list for multi-target support
echo "target_branches<<EOF" >> $GITHUB_OUTPUT
echo "$TARGET_BRANCHES" >> $GITHUB_OUTPUT
echo "EOF" >> $GITHUB_OUTPUT
echo "custom_topic=$CUSTOM_TOPIC" >> $GITHUB_OUTPUT

echo "Target branches: $(echo $TARGET_BRANCHES | tr '\n' ', ')"

# 2. THE CHAIN REACTION: If a topic label exists, find and tag sister PRs
if [ -n "$CUSTOM_TOPIC" ]; then
echo "Found topic label '$CUSTOM_TOPIC'. Searching for sister PRs to auto-trigger..."
ORG_NAME=$(echo "${{ github.repository }}" | cut -d'/' -f1)

# Find all merged PRs across the org sharing this exact topic label
SISTER_PRS=$(gh search prs --label "$CUSTOM_TOPIC" --owner "$ORG_NAME" --state closed --merged --limit 100 --json url,labels 2>/dev/null || echo "[]")

for row in $(echo "$SISTER_PRS" | jq -r '.[] | @base64'); do
_jq() { echo ${row} | base64 --decode | jq -r ${1}; }
SISTER_URL=$(_jq '.url')

# Skip the current PR (already running)
if [ "$SISTER_URL" == "$CURRENT_PR_URL" ]; then
echo "⏭️ Skipping self: $SISTER_URL"
continue
fi

# Propagate ALL target labels to sister PRs
while IFS= read -r BRANCH; do
[ -z "$BRANCH" ] && continue
LABEL_TO_ADD="cherry-pick to $BRANCH"

# Guard: skip if sister PR already has this label (prevents infinite loop)
EXISTING_LABELS=$(echo ${row} | base64 --decode | jq -r '.labels[].name' 2>/dev/null)
if echo "$EXISTING_LABELS" | grep -qF "$LABEL_TO_ADD"; then
echo "⏭️ Already labeled ($LABEL_TO_ADD): $SISTER_URL"
continue
fi

echo "🔗 Propagating '$LABEL_TO_ADD' to sister PR: $SISTER_URL"
SISTER_REPO=$(echo "$SISTER_URL" | sed -E 's|https://github.com/([^/]+/[^/]+)/pull/.*|\1|')
gh label create "$LABEL_TO_ADD" --repo "$SISTER_REPO" --color "d93f0b" --force >/dev/null 2>&1 || true
gh pr edit "$SISTER_URL" --add-label "$LABEL_TO_ADD" 2>/dev/null || echo "⚠️ Could not label $SISTER_URL (check token permissions)"
done <<< "$TARGET_BRANCHES"
done
fi

- name: Checkout Code
if: steps.parse_meta.outputs.target_branches != ''
uses: actions/checkout@v4
with:
fetch-depth: 0
token: ${{ secrets.CROSS_REPO_TOKEN || secrets.GITHUB_TOKEN }}

- name: Execute Cherry-Pick
if: steps.parse_meta.outputs.target_branches != ''
env:
GH_TOKEN: ${{ secrets.CROSS_REPO_TOKEN || secrets.GITHUB_TOKEN }}
TARGET_BRANCHES: ${{ steps.parse_meta.outputs.target_branches }}
CUSTOM_TOPIC: ${{ steps.parse_meta.outputs.custom_topic }}
PR_NUMBER: ${{ github.event.pull_request.number }}
PR_TITLE: ${{ github.event.pull_request.title }}
PR_URL: ${{ github.event.pull_request.html_url }}
PR_NUMBER_OVERRIDE: ${{ inputs.pr_number_override }}
REPO: ${{ github.repository }}
run: |
# Configure git
git config user.name "github-actions[bot]"
git config user.email "github-actions[bot]@users.noreply.github.com"

# When triggered via issues:labeled on an already-merged PR, pull_request context is empty
if [ -n "$PR_NUMBER_OVERRIDE" ] && [ -z "$PR_NUMBER" ]; then
PR_DATA=$(gh pr view "$PR_NUMBER_OVERRIDE" --repo "$REPO" --json title,url,mergeCommit,state)
if [ "$(echo "$PR_DATA" | jq -r '.state')" != "MERGED" ]; then
echo "PR #$PR_NUMBER_OVERRIDE is not yet merged. Skipping."
exit 0
fi
PR_NUMBER="$PR_NUMBER_OVERRIDE"
PR_TITLE=$(echo "$PR_DATA" | jq -r '.title')
PR_URL=$(echo "$PR_DATA" | jq -r '.url')
MERGE_SHA=$(echo "$PR_DATA" | jq -r '.mergeCommit.oid // empty')
fi

# Resolve commits that landed on base branch, handling all merge strategies
MERGE_SHA="${MERGE_SHA:-${{ github.event.pull_request.merge_commit_sha }}}"
if git cat-file -e "${MERGE_SHA}^2" 2>/dev/null; then
# Standard merge commit (2 parents): replay individual feature branch commits in order
COMMITS=$(git log --pretty=format:"%H" --reverse ${MERGE_SHA}^1..${MERGE_SHA}^2 2>/dev/null)
else
# Squash or rebase: derive commit count from PR API to walk back from merge SHA
PR_COMMIT_COUNT=$(gh pr view "$PR_NUMBER" --repo "$REPO" --json commits --jq '.commits | length' 2>/dev/null || echo "1")
COMMITS=$(git log --pretty=format:"%H" --reverse -"${PR_COMMIT_COUNT}" "${MERGE_SHA}" 2>/dev/null)
fi
if [ -z "$COMMITS" ]; then
COMMITS="$MERGE_SHA"
fi

# Process each target branch
while IFS= read -r TARGET_BRANCH; do
[ -z "$TARGET_BRANCH" ] && continue
echo ""
echo "=========================================="
echo "🎯 Cherry-picking to: $TARGET_BRANCH"
echo "=========================================="

CHERRY_PICK_BRANCH="cherry-pick-${PR_NUMBER}-to-$(echo $TARGET_BRANCH | sed 's|/|-|g')"

# Build backport label
BACKPORT_LABEL=""
if [ -n "$CUSTOM_TOPIC" ]; then
BRANCH_SUFFIX=$(echo "$TARGET_BRANCH" | sed 's|^support/||; s|^release/||; s|^feature/||')
BACKPORT_LABEL="${CUSTOM_TOPIC}_${BRANCH_SUFFIX}"
fi

# Verify target branch exists
if ! git fetch origin "$TARGET_BRANCH" 2>/dev/null; then
gh pr comment "$PR_URL" --body "$(printf '❌ **Cherry-pick failed:** Target branch \x60%s\x60 does not exist.\n\nPlease check the label for typos and ensure the branch has been created.' "$TARGET_BRANCH")"
echo "Error: Target branch '$TARGET_BRANCH' does not exist. Skipping."
continue
fi

# Create cherry-pick branch
git checkout -b "$CHERRY_PICK_BRANCH" "origin/$TARGET_BRANCH"

# Attempt cherry-pick; capture stderr to reliably distinguish empty vs conflict
CONFLICT=false
EMPTY=false
for COMMIT in $COMMITS; do
CHERRY_OUTPUT=$(git cherry-pick -x "$COMMIT" 2>&1) && CHERRY_EXIT=0 || CHERRY_EXIT=$?
if [ $CHERRY_EXIT -ne 0 ]; then
if echo "$CHERRY_OUTPUT" | grep -qiE "empty|nothing to commit|already applied"; then
EMPTY=true
git cherry-pick --abort 2>/dev/null || git reset --hard HEAD 2>/dev/null || true
else
CONFLICT=true
git cherry-pick --abort 2>/dev/null || true
fi
break
fi
done

if [ "$EMPTY" = "true" ]; then
gh pr comment "$PR_URL" --body "$(printf 'ℹ️ **Cherry-pick to \x60%s\x60 skipped:** The changes already exist on the target branch.\n\nNo action needed — this commit was likely already applied manually.' "$TARGET_BRANCH")"
echo "Cherry-pick skipped: changes already on $TARGET_BRANCH."
git checkout --detach 2>/dev/null; git branch -D "$CHERRY_PICK_BRANCH" 2>/dev/null || true
continue
fi

if [ "$CONFLICT" = "true" ]; then
LABEL_HINT=""
if [ -n "$BACKPORT_LABEL" ]; then
LABEL_HINT=$(printf '\n\n> ⚠️ **Important:** Add the \x60%s\x60 label to your manual PR. This is required for cross-repo cascade — without it, sister repositories will not be triggered for further cherry-picks from this branch.' "$BACKPORT_LABEL")
fi
gh pr comment "$PR_URL" --body "$(printf '⚠️ **Cherry-pick to \x60%s\x60 failed due to merge conflicts.**\n\nPlease resolve the conflicts manually and create a PR targeting \x60%s\x60.%s' "$TARGET_BRANCH" "$TARGET_BRANCH" "$LABEL_HINT")"
echo "Cherry-pick to $TARGET_BRANCH failed due to conflicts."
git checkout --detach 2>/dev/null; git branch -D "$CHERRY_PICK_BRANCH" 2>/dev/null || true
continue
fi

# Push with error handling so remaining branches are still processed on failure
if ! git push --force origin "$CHERRY_PICK_BRANCH" 2>/dev/null; then
echo "⚠️ Failed to push $CHERRY_PICK_BRANCH. Skipping PR creation for $TARGET_BRANCH."
git checkout --detach 2>/dev/null; git branch -D "$CHERRY_PICK_BRANCH" 2>/dev/null || true
continue
fi

# Ensure backport label exists in the repo before attaching it
if [ -n "$BACKPORT_LABEL" ]; then
gh label create "$BACKPORT_LABEL" --repo "$REPO" --color "0e8a16" --force >/dev/null 2>&1 || true
fi

# Create PR only if one doesn't already exist
EXISTING_PR=$(gh pr list --repo "$REPO" --head "$CHERRY_PICK_BRANCH" --state open --json number --jq '.[0].number // empty')
if [ -n "$EXISTING_PR" ]; then
echo "ℹ️ Cherry-pick PR #$EXISTING_PR already exists for $CHERRY_PICK_BRANCH. Updated branch."
git checkout --detach 2>/dev/null; git branch -D "$CHERRY_PICK_BRANCH" 2>/dev/null || true
continue
fi

if [ -n "$BACKPORT_LABEL" ]; then
gh pr create \
--repo "$REPO" \
--head "$CHERRY_PICK_BRANCH" \
--base "$TARGET_BRANCH" \
--title "$PR_TITLE" \
--body "Cherry-pick of #${PR_NUMBER} to \`$TARGET_BRANCH\`." \
--label "$BACKPORT_LABEL" || echo "⚠️ Failed to create PR for $TARGET_BRANCH."
else
gh pr create \
--repo "$REPO" \
--head "$CHERRY_PICK_BRANCH" \
--base "$TARGET_BRANCH" \
--title "$PR_TITLE" \
--body "Cherry-pick of #${PR_NUMBER} to \`$TARGET_BRANCH\`." || echo "⚠️ Failed to create PR for $TARGET_BRANCH."
fi

echo "✅ Cherry-pick PR created for $TARGET_BRANCH."
git checkout --detach 2>/dev/null; git branch -D "$CHERRY_PICK_BRANCH" 2>/dev/null || true
done <<< "$TARGET_BRANCHES"
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