---
features:
  - |
    Adds a ``base_pip_conf`` templating block for the base image, helping to
    customize pip settings used at build time for offline build scenarios. We
    need some required environment variables configured at the top level for
    all containers, for example the variable ``UPPER_CONSTRAINTS_FILE`` used by
    the ``bifrost-deploy`` installation scripts. Also here we can override the
    address of the PyPI repository via ``PIP_INDEX_URL``,
    ``PIP_EXTRA_INDEX_URL``, and ``PIP_TRUSTED_HOST`` variables.
upgrade:
  - |
    All Dockerfile files which uses curl to download any external files from the
    Internet now have a corresponding version templating block which can
    be used to override them. Also all the ENV instructions inside these blocks
    converted to the ARG instructions to minimize the unneeded variables.