push to container registry only from default branch

.gitlab-ci.yml

@@ -10,7 +10,14 @@ default:
   before_script:
     - echo "{\"auths\":{\"$CI_REGISTRY\":{\"username\":\"$CI_REGISTRY_USER\",\"password\":\"$CI_REGISTRY_PASSWORD\"}}}" > /kaniko/.docker/config.json
   script:
-    - /kaniko/executor --context dir://$CI_PROJECT_DIR/$CI_JOB_NAME --dockerfile $CI_PROJECT_DIR/$CI_JOB_NAME/Dockerfile --destination $CI_REGISTRY_IMAGE/$CI_JOB_NAME:latest
+    - /kaniko/executor --context dir://$CI_PROJECT_DIR/$CI_JOB_NAME --dockerfile $CI_PROJECT_DIR/$CI_JOB_NAME/Dockerfile $KANIKO_PUSH_POLICY
+  rules:
+    - if: $CI_COMMIT_BRANCH == $CI_DEFAULT_BRANCH
+      variables:
+        KANIKO_PUSH_POLICY: "--destination $CI_REGISTRY_IMAGE/$CI_JOB_NAME:latest"
+    - if: $CI_COMMIT_BRANCH != $CI_DEFAULT_BRANCH
+      variables:
+        KANIKO_PUSH_POLICY: "--no-push"
 
 centos8-eb-base:
   extends: .kaniko