Regular Debian produces "point release" CD images periodically that can be used in
/etc/apt/sources.list to update systems offline.
Is there any way to upgrade to a newer release of Raspbian in a similar fashion, e.g. from Buster 2019-06-20 to Buster 2019-07-10? I suspect there aren't any sort of pre-made images for this, but if there's a way to create a "portable update repository" myself (i.e. get a list of packages updated in the new release, download them all onto a USB drive somehow, and be able to
apt-get upgrade any Raspbian install from it), that would be ideal.