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

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Requiring undiverged branches in PRs

While PR locks prevent you from PRs stepping on eachother in parallel, they still do not protect you from a stale branch that is behind the current main head. In order to safeguard against this you have a few options: Force your repo to always have rebased branches from main. In github this is done by adding the branch protection rule: Under settings > branch protection rules > Require branches to be up to date before merging → check this Since digger will always query github api for mergability status, this protects you from any stale apply from PRs being performed. Understandably this may not be feasible to mark especially for monorepos that mix code and terraform. In such cases you can achieve a similar effect by using a custom workflow like below (digger.yml): 
projects:
- name: gcp-infra
  dir: cloud/terraform/gcp
  workflow: terraform-strict

workflows:
  terraform-strict:
    plan:
      steps:
        - run: |
            echo "Checking if branch is up-to-date with main..."
            git fetch --unshallow origin main || git fetch origin main
            git fetch --unshallow origin HEAD || git fetch origin HEAD
            if ! git merge-base --is-ancestor origin/main HEAD; then
              echo "❌ Branch is not up-to-date with main. Please rebase or merge main into your branch."
              echo "Run: git fetch origin && git rebase origin/main"
              exit 1
            fi
            echo "✅ Branch is up-to-date with main"
        - init
        - plan
    apply:
      steps:
        - run: |
            echo "Checking if branch is up-to-date with main..."
            git fetch --unshallow origin main || git fetch origin main
            git fetch --unshallow origin HEAD || git fetch origin HEAD
            if ! git merge-base --is-ancestor origin/main HEAD; then
              echo "❌ Branch is not up-to-date with main. Please rebase or merge main into your branch."
              echo "Run: git fetch origin && git rebase origin/main"
              exit 1
            fi
            echo "✅ Branch is up-to-date with main"
        - init
        - apply
We plan to eventually support this natively as a flag in digger