Add a gitlab CI script

.gitlab-ci.yml

+stages:
+  - test
+  - build
+  - release
+
+variables:
+  HUB_CONTAINER_PATH: "uplex/k8s-vcl-reloader"
+
+push_to_docker:
+  image: docker:20.10.9
+  stage: release
+  only:
+    - tags
+  services:
+    - docker:20.10.9-dind
+  script:
+    - docker login -u "$CI_REGISTRY_USER" -p "$CI_REGISTRY_PASSWORD" $CI_REGISTRY
+    - docker pull $CI_REGISTRY_IMAGE:$CI_COMMIT_REF_NAME
+    - docker tag $CI_REGISTRY_IMAGE:$CI_COMMIT_REF_NAME $HUB_CONTAINER_PATH:$CI_COMMIT_TAG
+    - docker login -u "$DOCKERHUB_USER" -p "$DOCKERHUB_CREDS"
+    - docker push $HUB_CONTAINER_PATH:$CI_COMMIT_TAG
+
+test:
+  image: golang:1.19
+  stage: test
+  rules:
+    - changes:
+      - cmd/**.go
+      - pkg/**.go
+      - go.mod
+      - go.sum
+  before_script:
+    - apt-get update -q
+    - apt-get install -y golang-golang-x-tools pandoc
+    - go get -d github.com/slimhazard/gogitversion
+    - pushd $GOPATH/pkg/mod/github.com/slimhazard/gogitversion*
+    - chmod a+x ./bootstrap.sh
+    - ./bootstrap.sh
+    - make install
+    - popd
+    - go get -u golang.org/x/lint/golint
+    - go mod download
+  script:
+    - make check
+
+# basic step for a pipeline to build the reloader image
+build:reloader:
+  extends: .build-image
+  stage: build
+  script:
+    - cd container
+    - make container
+
+.build-image:
+  stage: build
+  image: docker:20.10.9
+  services:
+    - docker:20.10.9-dind
+  before_script:
+    - apk add -U make
+    - docker login -u "$CI_REGISTRY_USER" -p "$CI_REGISTRY_PASSWORD" $CI_REGISTRY
+    - docker pull $CI_REGISTRY_IMAGE:$CI_COMMIT_REF_NAME || true
+  after_script:
+    - docker tag $CI_REGISTRY_IMAGE $CI_REGISTRY_IMAGE:$CI_COMMIT_SHA
+    - docker tag $CI_REGISTRY_IMAGE $CI_REGISTRY_IMAGE:$CI_COMMIT_REF_NAME
+    - docker push $CI_REGISTRY_IMAGE:$CI_COMMIT_SHA
+    - docker push $CI_REGISTRY_IMAGE:$CI_COMMIT_REF_NAME