Add nx-set-shas step

.github/workflows/ci.yml

@@ -61,6 +61,9 @@ jobs:
           fetch-depth: 0
       - name: Install dependencies
         run: yarn install --frozen-lockfile
+      # Set convenience variables. Source: https://nx.dev/ci/recipes/set-up/monorepo-ci-github-actions#get-the-commit-of-the-last-successful-build
+      - name: Derive appropriate SHAs for base and head for `nx affected` commands
+        uses: nrwl/nx-set-shas@v4
       # This step is relevant for docker images. Right now we use a managed environment in GCP App Engine.
       - name: Authenticate to Google Cloud
         uses: "google-github-actions/auth@v0.4.0"