Use git status to check for changes to devsite (#8448)

Author: dlarocque

.github/workflows/check-docs.yml

@@ -36,7 +36,12 @@ jobs:
     - name: Run doc generation
       run: yarn docgen:all
     - name: Check for changes in docs-devsite dir (fail if so)
-      run: git diff --exit-code docs-devsite
+      run: |
+        if [[ -n "$(git status docs-devsite --porcelain)" ]]; then
+          echo "Unstaged changes detected:"
+          git status -s
+          exit 1
+        fi
     - name: Reference documentation needs to be updated. See message below.
       if: ${{ failure() }}
       run: echo "Changes in this PR affect the reference docs. Run \`yarn docgen:all\` locally to regenerate docs and add them to this PR."