packaging.py 文件源码

def get_version(package_name, pre_version=None):
    """Get the version of the project. First, try getting it from PKG-INFO, if
    it exists. If it does, that means we're in a distribution tarball or that
    install has happened. Otherwise, if there is no PKG-INFO file, pull the
    version from git.

    We do not support setup.py version sanity in git archive tarballs, nor do
    we support packagers directly sucking our git repo into theirs. We expect
    that a source tarball be made from our git repo - or that if someone wants
    to make a source tarball from a fork of our repo with additional tags in it
    that they understand and desire the results of doing that.
    """
    version = os.environ.get(
        "PBR_VERSION",
        os.environ.get("OSLO_PACKAGE_VERSION", None))
    if version:
        return version
    version = _get_version_from_pkg_info(package_name)
    if version:
        return version
    version = _get_version_from_git(pre_version)
    # Handle http://bugs.python.org/issue11638
    # version will either be an empty unicode string or a valid
    # unicode version string, but either way it's unicode and needs to
    # be encoded.
    if sys.version_info[0] == 2:
        version = version.encode('utf-8')
    if version:
        return version
    raise Exception("Versioning for this project requires either an sdist"
                    " tarball, or access to an upstream git repository."
                    " Are you sure that git is installed?")


# This is added because pbr uses pbr to install itself. That means that
# any changes to the egg info writer entrypoints must be forward and
# backward compatible. This maintains the pbr.packaging.write_pbr_json
# path.