ci(observability-map): scan head vs merge base and upsert a sticky PR comment

Author: 1stvamp

.github/workflows/observability-map.yml

@@ -0,0 +1,78 @@
+name: 🗺️ Observability Map
+
+on:
+  pull_request:
+    types: [opened, synchronize, reopened]
+    paths:
+      - "apps/webapp/app/routes/**"
+      - "internal-packages/observability-map/**"
+
+concurrency:
+  group: observability-map-${{ github.event.pull_request.number }}
+  cancel-in-progress: true
+
+permissions:
+  contents: read
+  pull-requests: write
+
+jobs:
+  report:
+    runs-on: warp-ubuntu-latest-x64-4x
+    # Fork PRs get a read-only token, so the comment cannot post. Skipping the job beats a red x.
+    if: github.event.pull_request.head.repo.full_name == github.repository
+    steps:
+      - name: ⬇️ Checkout repo
+        uses: actions/checkout@9c091bb21b7c1c1d1991bb908d89e4e9dddfe3e0 # v7.0.0
+        with:
+          fetch-depth: 0
+          persist-credentials: false
+
+      - name: ⎔ Setup pnpm
+        uses: pnpm/action-setup@fc06bc1257f339d1d5d8b3a19a8cae5388b55320 # v5.0.0
+        with:
+          version: 10.33.2
+
+      - name: ⎔ Setup node
+        uses: WarpBuilds/setup-node@bc639b444d583175926b588962199c247d23e8d3 # v6
+        with:
+          node-version: 24.18.0
+          cache: "pnpm"
+
+      - name: 📥 Download deps
+        run: pnpm install --frozen-lockfile
+
+      - name: 🔎 Scan head
+        run: |
+          pnpm --filter @internal/observability-map exec tsx src/cli.ts --json --no-write > /tmp/head.json
+
+      - name: 🔎 Scan base with the head's scanner
+        run: |
+          if git worktree add /tmp/base-tree ${{ github.event.pull_request.base.sha }} \
+            && pnpm --filter @internal/observability-map exec tsx src/cli.ts --json --no-write \
+              --routes=/tmp/base-tree/apps/webapp/app/routes > /tmp/base.json; then
+            :
+          else
+            echo "-" > /tmp/base.json || true
+            echo "base scan failed or the worktree could not be added; falling back to no base" >&2
+          fi
+
+      - name: 📝 Render comment
+        run: |
+          if [ "$(cat /tmp/base.json)" = "-" ]; then
+            pnpm --filter @internal/observability-map exec tsx src/report/prCommentCli.ts /tmp/head.json - > /tmp/comment.md
+          else
+            pnpm --filter @internal/observability-map exec tsx src/report/prCommentCli.ts /tmp/head.json /tmp/base.json > /tmp/comment.md
+          fi
+
+      - name: 💬 Upsert PR comment
+        env:
+          GH_TOKEN: ${{ github.token }}
+          PR_NUMBER: ${{ github.event.pull_request.number }}
+        run: |
+          existing=$(gh api "repos/${GITHUB_REPOSITORY}/issues/${PR_NUMBER}/comments" --paginate \
+            --jq '[.[] | select(.body | startswith("<!-- observability-map-report -->"))][0].id // empty')
+          if [ -n "$existing" ]; then
+            gh api -X PATCH "repos/${GITHUB_REPOSITORY}/issues/comments/${existing}" -F body=@/tmp/comment.md
+          else
+            gh api "repos/${GITHUB_REPOSITORY}/issues/${PR_NUMBER}/comments" -F body=@/tmp/comment.md
+          fi