Digger currently does not support apply_requirements (like in Atlantis). Coming soon - (#1252)

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Workaround

You can use mergeability requirements together with Status Checks to achieve the same. Digger will not apply if the pull request is not in a “mergeable” state as specified by GitHub api. This means that if you have a separate status check and you have this check as “required” by branch protection rules then an attempt of digger apply will not go ahead. Note: there is a known issue that would cause the “mergability” check to conflict if you set the digger/apply check as required on github. We are working on a fix and in the meantime you have an option to turn off the mergability check if you want to have this digger/apply check as required. You can turn it off in the workflow configuration by setting the skip_merge_check flag as follows (we have to set the other configurations since they are currently required): 
projects:
- name: dev
  dir: dev
  workflow: mydev

workflows:
  mydev:
    workflow_configuration:
      on_pull_request_pushed: ["digger plan"]
      on_pull_request_closed: ["digger unlock"]
      on_commit_to_default: ["digger unlock"]
      skip_merge_check: true