message: Fix image acquisition when CI is run outside of a pull request
diff: set -uex
  -if [[ $# -ne 1 ]]; then
  - echo "Usage: ci-output-build-image <base revision commit hash>"
  - exit 1
  +if [[ $# -eq 1 ]]; then
  + # If a base revision is given as an argument, use it
  + BASE_REVISION="$1"
  +else
  + # Otherwise, for the use-case where CI is being run directly on the main branch
  + # without a pull request, use the commit hash of HEAD
  + BASE_REVISION="$(git rev-parse HEAD)"
  fi
  -BASE_REVISION="$1"
  SCRIPT_PATH="$(realpath "$(dirname "$0")")"
  "${SCRIPT_PATH}/acquire-base-image" --nothing-or-local-if-changed "${BASE_REVISION}"
  