CI/CD patterns with parent-child and multi-project pipelines

This post introduces and explains the concepts of parent-child pipelines and multi-project pipelines in GitLab CI/CD. It details how parent-child pipelines help manage complexity within a monorepo by breaking down monolithic pipelines into isolated child pipelines for different components (e.g., UI, backend), allowing for independent management and execution. It also explains multi-project pipelines as a mechanism to chain together pipelines from separate repositories, enabling verification of integration between independent components and triggering downstream deployments. Key differences in context, control, side-effects, and visibility between the two pipeline types are highlighted, along with planned future developments for parent-child pipelines.