Automatically deploy to Firebase with Gitlab CI - https://medium.com/evenbit/automatically-deploy-to-firebase-with-gitlab-ci-546f194c44d8

.gitlab-ci.yml

image: node:latest

cache:
  paths:
    - node_modules/
    - app/bower_components

deploy_production:
  stage: deploy
  environment: Production
  only:
    - master
  script:
    - npm install -g firebase-tools
    - npm install -g bower
    - npm install
    - bower install --allow-root
    - firebase use --token $FIREBASE_DEPLOY_KEY production
    - firebase deploy -m "Pipeline $CI_PIPELINE_ID, build $CI_BUILD_ID" --non-interactive --token $FIREBASE_DEPLOY_KEY