How can you ensure that developers can only create scratch orgs from Git packages?

Selecting Git Packages in the Copado DX Mode picklist field is the correct approach to ensure that developers can only create scratch orgs from Git packages. When this option is enabled, it effectively sets the context for scratch org creation to be tightly integrated with the version control system, linking it directly to the packages stored in Git. This enforces best practices by ensuring that any scratch org created will be based on specific, versioned Git packages, facilitating better collaboration and reduces the risk of divergent or untracked code changes.

The other choices do not specifically control the creation of scratch orgs based on Git packages. Setting permissions might manage who can create scratch orgs but does not restrict the source of the org creation to Git packages. Limiting access to older branches is more focused on branch management rather than directly controlling scratch org creation. Similarly, configuring the YAML for the pipeline is important for CI/CD configurations but does not define the source from which scratch orgs can be created. Therefore, choosing the Git Packages option directly addresses the requirement of managing scratch org sources.