$CI_COMMIT_TAG is empty when job runs

Hello,

I want to have the tag referencing the last git commit available in my gitlab-ci.yml script using $CI_COMMIT_TAG.

But every time the job runs the echo $CI_COMMIT_TAG does not display nothing. The $CI_COMMIT_TAG seems to be empty.

The following is my gitlab-ci.yml.

stages:
  - build

build-dev:
  stage: build
  environment: development
  only:
    - master
  script
    - echo $CI_COMMIT_TAG

And toes are the git command I use to push with a tag.

git commit -am "test push with tag"
git tag test-tag
git push --tags origin master