Use IMAGE:latest as cache-from source for non-master builds

Non-master builds are not pushed, so we can only use the master builds
as cache.

.gitlab-ci.yml

@@ -51,20 +51,20 @@ build:
     - docker login -u "$CI_REGISTRY_USER" -p "$CI_REGISTRY_PASSWORD" $CI_REGISTRY
   script:
     - IMAGE="$CI_REGISTRY_IMAGE/pvs_core"
-    - docker pull "$IMAGE":$CI_COMMIT_REF_NAME || true
-    - docker build --cache-from "$IMAGE":$CI_COMMIT_REF_NAME -t "$IMAGE":$CI_COMMIT_REF_SLUG -t "$IMAGE":$CI_COMMIT_REF_NAME core/
+    - docker pull "$IMAGE":latest || true
+    - docker build --cache-from "$IMAGE":latest -t "$IMAGE":$CI_COMMIT_REF_SLUG -t "$IMAGE":$CI_COMMIT_REF_NAME core/
     - docker tag "$IMAGE:$CI_COMMIT_REF_NAME" "$IMAGE:latest"
     - IMAGE="$CI_REGISTRY_IMAGE/pvs_preprocessor"
-    - docker pull "$IMAGE":$CI_COMMIT_REF_NAME || true
-    - docker build --cache-from "$IMAGE":$CI_COMMIT_REF_NAME -t "$IMAGE":$CI_COMMIT_REF_SLUG -t "$IMAGE":$CI_COMMIT_REF_NAME preprocessor/
+    - docker pull "$IMAGE":latest || true
+    - docker build --cache-from "$IMAGE":latest -t "$IMAGE":$CI_COMMIT_REF_SLUG -t "$IMAGE":$CI_COMMIT_REF_NAME preprocessor/
     - docker tag "$IMAGE:$CI_COMMIT_REF_NAME" "$IMAGE:latest"
     - IMAGE="$CI_REGISTRY_IMAGE/pvs_client"
-    - docker pull "$IMAGE":$CI_COMMIT_REF_NAME || true
-    - docker build --cache-from "$IMAGE":$CI_COMMIT_REF_NAME -t "$IMAGE":$CI_COMMIT_REF_SLUG -t "$IMAGE":$CI_COMMIT_REF_NAME client/
+    - docker pull "$IMAGE":latest || true
+    - docker build --cache-from "$IMAGE":latest -t "$IMAGE":$CI_COMMIT_REF_SLUG -t "$IMAGE":$CI_COMMIT_REF_NAME client/
     - docker tag "$IMAGE:$CI_COMMIT_REF_NAME" "$IMAGE:latest"
     - IMAGE="$CI_REGISTRY_IMAGE/pvs_cache"
-    - docker pull "$IMAGE":$CI_COMMIT_REF_NAME || true
-    - docker build --cache-from "$IMAGE":$CI_COMMIT_REF_NAME -t "$IMAGE":$CI_COMMIT_REF_SLUG -t "$IMAGE":$CI_COMMIT_REF_NAME cache/
+    - docker pull "$IMAGE":latest || true
+    - docker build --cache-from "$IMAGE":latest -t "$IMAGE":$CI_COMMIT_REF_SLUG -t "$IMAGE":$CI_COMMIT_REF_NAME cache/
     - docker tag "$IMAGE:$CI_COMMIT_REF_NAME" "$IMAGE:latest"
     - chmod +x gitlab_test.sh
     - ./gitlab_test.sh