Upgrades all packages via ``apk upgrade`` or a specific package if name or
    pkgs is specified. Name is ignored if pkgs is specified

    Returns a dict containing the changes.

        {'<package>':  {'old': '<old-version>',
                        'new': '<new-version>'}}

    CLI Example:

    .. code-block:: bash

        salt '*' pkg.upgrade

def upgrade(name=None, pkgs=None, refresh=True, **kwargs):
    '''
    Upgrades all packages via ``apk upgrade`` or a specific package if name or
    pkgs is specified. Name is ignored if pkgs is specified

    Returns a dict containing the changes.

        {'<package>':  {'old': '<old-version>',
                        'new': '<new-version>'}}

    CLI Example:

    .. code-block:: bash

        salt '*' pkg.upgrade
    '''
    ret = {'changes': {},
           'result': True,
           'comment': '',
           }

    if salt.utils.data.is_true(refresh):
        refresh_db()

    old = list_pkgs()

    pkg_to_upgrade = []

    if name and not pkgs:
        if ',' in name:
            pkg_to_upgrade = name.split(',')
        else:
            pkg_to_upgrade = [name]

    if pkgs:
        pkg_to_upgrade.extend(pkgs)

    if pkg_to_upgrade:
        cmd = ['apk', 'add', '-u']
        cmd.extend(pkg_to_upgrade)
    else:
        cmd = ['apk', 'upgrade']

    call = __salt__['cmd.run_all'](cmd,
                                   output_loglevel='trace',
                                   python_shell=False,
                                   redirect_stderr=True)

    if call['retcode'] != 0:
        ret['result'] = False
        if call['stdout']:
            ret['comment'] = call['stdout']

    __context__.pop('pkg.list_pkgs', None)
    new = list_pkgs()
    ret['changes'] = salt.utils.data.compare_dicts(old, new)

    return ret