Try to force dockerhub push

It won't rebuild the image. All it does is push it

.dockerignore

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+# CI cache folder storing docker images
+ci-exports/
+
+.gitlab-ci.yml

.gitlab-ci.yml

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+image: docker:19.03.12
+
+stages:
+  - docker_test
+  - docker_push
+
+variables:
+  # When using dind service, we need to instruct docker to talk with
+  # the daemon started inside of the service. The daemon is available
+  # with a network connection instead of the default
+  # /var/run/docker.sock socket. Docker 19.03 does this automatically
+  # by setting the DOCKER_HOST in
+  # https://github.com/docker-library/docker/blob/d45051476babc297257df490d22cbd806f1b11e4/19.03/docker-entrypoint.sh#L23-L29
+  #
+  # The 'docker' hostname is the alias of the service container as described at
+  # https://docs.gitlab.com/ee/ci/docker/using_docker_images.html#accessing-the-services.
+  #
+  # Specify to Docker where to create the certificates, Docker will
+  # create them automatically on boot, and will create
+  # `/certs/client` that will be shared between the service and job
+  # container, thanks to volume mount from config.toml
+  DOCKER_TLS_CERTDIR: "/certs"
+  # Use TLS https://docs.gitlab.com/ee/ci/docker/using_docker_build.html#tls-enabled
+  DOCKER_HOST: tcp://docker:2376
+
+.docker_cache:
+  cache:
+    key: "$CI_COMMIT_REF_SLUG"
+    paths:
+      - ci-exports/*.tar
+
+services:
+  - docker:19.03.12-dind
+
+
+# Make sure we can build a docker image
+# It's pushed to the pipeline-local registry which acts as a cache
+build_docker:
+  extends:
+    - .docker_cache
+  stage: docker_test
+  script:
+    # Try to load latest branch image from local tar or from registry
+    - docker load ci-exports/$CI_COMMIT_REF_SLUG.tar || docker pull $CI_REGISTRY_IMAGE:latest || true
+    - docker build --cache-from $CI_REGISTRY_IMAGE:latest --tag $CI_REGISTRY_IMAGE:latest .
+    - mkdir -p ci-exports/
+    - docker save $CI_REGISTRY_IMAGE:latest > ci-exports/$CI_COMMIT_REF_SLUG.tar
+
+# Publishes the configured CI registry (by default that's gitlab's registry)
+push_ci_registry:
+  extends:
+    - .docker_cache
+  stage: docker_push
+  cache:
+    policy: pull
+  before_script:
+    - docker login -u $CI_REGISTRY_USER -p $CI_REGISTRY_PASSWORD $CI_REGISTRY
+  script:
+    - cat ci-exports/$CI_COMMIT_REF_SLUG.tar | docker load
+    - docker tag $CI_REGISTRY_IMAGE:latest $CI_REGISTRY_IMAGE:$CI_COMMIT_TAG
+    - docker push $CI_REGISTRY_IMAGE:$CI_COMMIT_TAG
+    - docker push $CI_REGISTRY_IMAGE:latest
+  only:
+    refs:
+      - master
+    variables:
+      - $CI_REGISTRY_USER
+      - $CI_REGISTRY_PASSWORD
+      - $CI_REGISTRY
+      - $CI_REGISTRY_IMAGE
+
+# Publishes the cached image to docker
+push_dockerhub_registry:
+  extends:
+    - .docker_cache
+  stage: docker_push
+  cache:
+    policy: pull
+  before_script:
+    - docker login -u $DOCKERHUB_REGISTRY_USER -p $DOCKERHUB_REGISTRY_PASSWORD $DOCKERHUB_REGISTRY
+  script:
+    - cat ci-exports/$CI_COMMIT_REF_SLUG.tar | docker load
+    - docker tag $CI_REGISTRY_IMAGE:latest $DOCKERHUB_REGISTRY_IMAGE:$CI_COMMIT_TAG
+    - docker tag $CI_REGISTRY_IMAGE:latest $DOCKERHUB_REGISTRY_IMAGE:latest
+    - docker push $DOCKERHUB_REGISTRY_IMAGE:$CI_COMMIT_TAG
+    - docker push $DOCKERHUB_REGISTRY_IMAGE:latest
+  only:
+    refs:
+#      - master
+      - tags
+    variables:
+      - $DOCKERHUB_REGISTRY_USER
+      - $DOCKERHUB_REGISTRY_PASSWORD
+      - $DOCKERHUB_REGISTRY
+      - $DOCKERHUB_REGISTRY_IMAGE