It would be useful for low bandwidth users to have a 'cache-only-upgrade'
Apt can already do that using:
apt-get --no-download --ignore-missing upgrade
...I'm not sure how to make that work for 'cupt', without running both
'cupt update' and 'apt-get update' regularly. To save bandwidth I'd
rather avoid running 'apt-get update'; also, keeping 'apt-get' in sync
with 'cupt' can be difficult.
Application: suppose a 400M (modem) upgrade needs 24 hours at 5K/sec, but
bandwidth is only available late at night, say 8 hours. In the
morning, some packages can usually be upgraded, (since their
dependencies have all been fetched), but which packages? Then at the
end of 3 days, there's new updates, and catching up can be delayed
In the meantime, for users who don't mind a (quite slow) kludge, this
seems to work:
# get 'cupt' to just upgrade only what's in the cache.
# parse upgradeable cached .deb files for '0B', make
# a list, and install with 'cupt'.
cupt -y iii `cupt -d -y safe-upgrade 2> /dev/null | \
grep -A 2 "The following packages will be upgraded" | \
tail -n 1 | tr ' ' '' | \
while read p ; do \
yes q | cupt iii $p 2> /dev/null | \
grep -q "get 0B" && echo -n $p" " ; \