GitLab CI & Git Integration

One-Sentence Understanding

GitLab CI/CD treats Git as the single source of truth for your entire DevOps lifecycle, from pipeline triggers triggered by pushes to automatic deployment triggered by tags.

Pipeline Triggers

GitLab CI can be triggered by various Git events:

workflow:
  rules:
    - if: $CI_PIPELINE_SOURCE == "push"
    - if: $CI_PIPELINE_SOURCE == "merge_request_event"
    - if: $CI_PIPELINE_SOURCE == "tag"
    - if: $CI_COMMIT_TAG

Branch-Specific Rules

stages:
  - test
  - deploy

test:
  stage: test
  script: npm test

deploy:
  stage: deploy
  script: npm run deploy
  rules:
    - if: $CI_COMMIT_BRANCH == "main"
    - if: $CI_COMMIT_TAG

Git Strategy in CI

GIT_STRATEGY Options

variables:
  GIT_STRATEGY: fetch
  GIT_DEPTH: "50"       # Shallow clone for speed
  GIT_SUBMODULE_STRATEGY: recursive

GitLab CI Variables from Git

GitLab provides rich CI/CD variables derived from Git:

script:
  # Commit info
  - echo "Commit: $CI_COMMIT_SHA"
  - echo "Short SHA: $CI_COMMIT_SHORT_SHA"
  - echo "Branch: $CI_COMMIT_BRANCH"
  - echo "Tag: $CI_COMMIT_TAG"
  - echo "Message: $CI_COMMIT_MESSAGE"

  # Author info
  - echo "Author: $GITLAB_USER_NAME"
  - echo "Email: $GITLAB_USER_EMAIL"

  # Merge request info
  - echo "MR: $CI_MERGE_REQUEST_IID"
  - echo "Source branch: $CI_MERGE_REQUEST_SOURCE_BRANCH_NAME"

Running Git Commands

before_script:
  - git config user.name "gitlab-ci"
  - git config user.email "ci@gitlab.com"

script:
  - git fetch --tags origin
  - VERSION=$(git describe --tags --abbrev=0 2>/dev/null || echo "v0.0.0")
  - echo "Current version: $VERSION"

CI_JOB_TOKEN

GitLab provides CI_JOB_TOKEN for authenticating Git operations:

# Push to a different repository
script:
  - git remote add target https://gitlab-ci-token:${CI_JOB_TOKEN}@gitlab.com/org/target.git
  - git push target main

Token Scope

Workflow Rules

Control pipeline execution based on Git context:

workflow:
  rules:
    - if: $CI_COMMIT_TAG
      variables:
        PIPELINE_TYPE: "release"
    - if: $CI_COMMIT_BRANCH == "main"
      variables:
        PIPELINE_TYPE: "deploy"
    - if: $CI_MERGE_REQUEST_ID
      variables:
        PIPELINE_TYPE: "merge_request"
    - when: always

Environment Management

GitLab Maps Git branches and tags to environments:

deploy_staging:
  stage: deploy
  script: deploy-to-staging
  environment:
    name: staging
    url: https://staging.example.com
    deployment_tier: staging
  rules:
    - if: $CI_COMMIT_BRANCH == "develop"

deploy_production:
  stage: deploy
  script: deploy-to-prod
  environment:
    name: production
    url: https://example.com
    deployment_tier: production
  rules:
    - if: $CI_COMMIT_TAG

Continue Learning

1. github/github-actions-basics — GitHub Actions basics
2. security/ssh-key-management — SSH key management
3. migration/svn-to-git — SVN to Git migration