pull docker image before building

.github/workflows/main.yml

@@ -10,7 +10,7 @@ name: CI Matrix
 on:
   pull_request:
   push:
-    branches: [master, dwest/test-docker]
+    branches: [master, dm/test-docker]
 
 jobs:
   docker:
@@ -26,6 +26,18 @@ jobs:
           git config --global url."https://".insteadOf "git://"
           git submodule update --init
 
+      - name: Artifactory Login
+        uses: docker/login-action@v2
+        with:
+          registry: artifactory.galois.com:5025
+          username: ${{ secrets.ARTIFACTORY_USER }}
+          password: ${{ secrets.ARTIFACTORY_KEY }}
+
+      # Pulls the latest image to try to re-use some layers
+      - name: Pull Latest Docker image
+        run: |
+          docker pull artifactory.galois.com:5025/pate/pate:latest
+
       - name: Build Docker Image
         run: |
           docker build . -t pate
@@ -35,13 +47,6 @@ jobs:
           docker run --rm -itd --entrypoint bash --name pate -v `pwd`/tests/aarch32:/tests pate
           (echo "cabal run pate-test-aarch32 -- -p args-equal") | script -q /dev/null docker attach pate
 
-      - name: Artifactory Login
-        uses: docker/login-action@v2
-        with:
-          registry: artifactory.galois.com:5025
-          username: ${{ secrets.ARTIFACTORY_USER }}
-          password: ${{ secrets.ARTIFACTORY_KEY }}
-
       - name: Push Docker image
         run: |
           CI_COMMIT_SHORT_SHA=$(git rev-parse --short $GITHUB_SHA)