ci: Request TW review from the PR's team label

.github/workflows/request-tw-review.yaml

@@ -0,0 +1,82 @@
+name: Request TW review by label
+
+on:
+  # Runs from master with a write token, so fork PRs work too. Never check out PR code here.
+  pull_request_target:
+    types: [opened, labeled, ready_for_review]
+
+permissions:
+  pull-requests: write
+
+jobs:
+  request_review:
+    name: Request TW review
+    # Like CODEOWNERS: no requests on drafts or closed PRs
+    if: github.event.action != 'opened' && github.event.pull_request.state == 'open' && !github.event.pull_request.draft
+    runs-on: ubuntu-latest
+    steps:
+      - name: Request the writer for the team label
+        env:
+          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+          GH_REPO: ${{ github.repository }}
+          # The new label, or all labels when a draft becomes ready
+          LABELS: ${{ github.event.action == 'labeled' && github.event.label.name || join(github.event.pull_request.labels.*.name, ' ') }}
+          PR_NUMBER: ${{ github.event.pull_request.number }}
+          PR_AUTHOR: ${{ github.event.pull_request.user.login }}
+        run: |
+          set -f  # label names are not globs
+          reviewers=""
+          for label in $LABELS; do
+            # Team labels → R&D group → technical writer
+            case "$label" in
+              t-core-services|t-infra|t-console|t-unblocking) reviewer=TC-MO ;;  # Foundation
+              t-publishers|t-billing|t-tooling|t-builders|"t-c&c") reviewer=szaganek ;;  # Creators
+              t-acquisition|t-growth|t-ai|t-integrations|t-discovery) reviewer=marcel-rbro ;;  # Integrators
+              *) continue ;;
+            esac
+            # GitHub rejects a review request from the PR author
+            [ "$reviewer" = "$PR_AUTHOR" ] && continue
+            case ",$reviewers," in
+              *",$reviewer,"*) ;;
+              *) reviewers="${reviewers:+$reviewers,}$reviewer" ;;
+            esac
+          done
+
+          if [ -z "$reviewers" ]; then
+            echo "No writer to request for: $LABELS"
+            exit 0
+          fi
+
+          gh pr edit "$PR_NUMBER" --add-reviewer "$reviewers"
+
+  fallback:
+    name: Request triage TW when no writer is set
+    # PRs from writers and bots need no triage
+    if: >-
+      (github.event.action == 'opened' || github.event.action == 'ready_for_review')
+      && !github.event.pull_request.draft
+      && github.event.pull_request.user.type != 'Bot'
+      && !contains(fromJSON('["TC-MO", "szaganek", "marcel-rbro"]'), github.event.pull_request.user.login)
+    runs-on: ubuntu-latest
+    steps:
+      - name: Request TC-MO if no writer was requested
+        env:
+          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+          GH_REPO: ${{ github.repository }}
+          PR_NUMBER: ${{ github.event.pull_request.number }}
+        run: |
+          # The PR toolkit adds the team label 20-30 s after the PR is ready; give the label job time to run
+          sleep 90
+
+          writers=$(gh pr view "$PR_NUMBER" --json reviewRequests,reviews,state,isDraft --jq '
+            if .state != "OPEN" or .isDraft then "skip"
+            else [.reviewRequests[].login, .reviews[].author.login]
+              | map(select(. == "TC-MO" or . == "szaganek" or . == "marcel-rbro")) | join(",")
+            end')
+
+          if [ -n "$writers" ]; then
+            echo "Nothing to do: $writers"
+            exit 0
+          fi
+
+          gh pr edit "$PR_NUMBER" --add-reviewer TC-MO