ci: ensure the shas used by compare match the current PR

Author: castastrophe

.github/workflows/development.yml

@@ -67,14 +67,45 @@ jobs:
             experimental: ${{ matrix.experimental }}
         secrets: inherit
 
+    # -------------------------------------------------------------
+    # Get the NX-blessed base and head shas.
+    # --------------------------------------------------------------
+    get-shas:
+        runs-on: ubuntu-latest
+        name: Get SHA values
+        outputs:
+            base-sha: ${{ steps.set-SHAs.outputs.base }}
+            head-sha: ${{ steps.set-SHAs.outputs.head }}
+        permissions:
+            pull-requests: read
+        steps:
+            - name: Check out code
+              uses: actions/checkout@v4
+              with:
+                  fetch-depth: 0
+
+            - name: Use Node LTS version
+              uses: actions/setup-node@v4
+              with:
+                  node-version: 18
+                  cache: yarn
+
+            - name: Derive appropriate SHAs for base and head for `nx affected` commands
+              id: set-SHAs
+              uses: nrwl/nx-set-shas@v3
+
     # -------------------------------------------------------------
     # Compare the compiled assets
     # -------------------------------------------------------------
     compare:
         name: Compare
+        needs: [get-shas]
         # Check that the PR is not in draft mode (or if it is, that it has the run_ci label to force a build)
         if: ${{ github.event.pull_request.draft != 'true' || contains(github.event.pull_request.labels.*.name, 'run_ci') }}
         uses: ./.github/workflows/compare-results.yml
+        with:
+            base-sha: ${{ needs.get-shas.outputs.base-sha }}
+            head-sha: ${{ needs.get-shas.outputs.head-sha }}
         secrets: inherit
 
     # -------------------------------------------------------------