update on label

gistfile1.txt

pull_request_rules:
  # If a a pull request has this label, try to update it
  - name: update on label
    conditions:
      - label=needs-update
    actions:
      update:

  # If a PR is up-to-date, make sure it does not have the `needs-update` label
  - name: clear update label
    conditions:
      - #commits-behind=0
    actions:
      label:
         remove:
            - needs-update