You can specify custom steps using the workflows section in digger.yml. Handy for integration with other CLIs like infracost. 
projects:
- name: production
  dir: prod
  workflow: with-infracost

workflows:
  with-infracost:
    plan:
      steps:
        - init
        - plan
        - run: infracost breakdown --path=. | tee -a $DIGGER_OUT

​
Environment variables

Digger makes the following environment variables available to custom commands:
  • $DEFAULT_BRANCH
  • $DIGGER_OUT
  • $PR_BRANCH
  • $PROJECT_NAME
  • $DIGGER_PLANFILE (the path where terraform plan file should be written)
These can be used to achieve workflows like infracost diff

​
$DIGGER_OUT

If your custom command writes into a file path defined in the $DIGGER_OUT env variable, then its content will be appended to the comment as “additional output”: The value of $DIGGER_OUT defaults to $RUNNER_TEMP/digger-out.log; you can change that if needed by setting the env var explicitly.