Custom actions for XGBoost

XGBoost implements a few custom composite actions to reduce duplicated code within workflow YAML files. The custom actions are hosted in a separate repository, dmlc/xgboost-devops, to make it easy to test changes to the custom actions in a pull request or a fork.

In a workflow file, we'd refer to dmlc/xgboost-devops/{custom-action}@main. For example:

- uses: dmlc/xgboost-devops/miniforge-setup@main
  with:
    environment-name: cpp_test
    environment-file: ops/conda_env/cpp_test.yml

Each custom action consists of two components:

• Main script (dmlc/xgboost-devops/{custom-action}/action.yml): dispatches to a specific version of the implementation script (see the next item). The main script clones xgboost-devops from a specified fork at a particular ref, allowing us to easily test changes to the custom action.
• Implementation script (dmlc/xgboost-devops/impls/{custom-action}/action.yml): Implements the custom script.

This design was inspired by Mike Sarahan's work in rapidsai/shared-actions.