.gitlab-ci.yml

stages:
    - build

build_badges:
  stage: build
  tags:
    - docker-build
  before_script:
    - chmod +x get-updated-badge-info.sh
  script:
    - echo "Some script to build your code"
  after_script:
    - ./get-updated-badge-info.sh
  artifacts:
    paths:
        - badges.json
    when: always
    expire_in: 4 weeks

get-updated-badge-info.sh

#!/bin/bash

echo "collecting stas for badges"

commits=`git rev-list --all --count`
latest_release_tag=$(git describe --tags `git rev-list --tags --max-count=1`)
echo "{\"commits\":\"$commits\", \"release_tag"\:\"$latest_release_tag\"}" > badges.json

I have made a sample repository here: https://gitlab.com/asdoi/gitlab_badges_sample