Comment 17 for bug 127263

For an example of when the patch isn't good enough:

# make sure we don't already know about gutsy or have the problematic empty file
sudo rm /var/lib/update-manager/meta-release
sudo update-manager -c
# Close, then:
sudo update-manager -d

/var/lib/update-manager/meta-release created by update-manager -c won't have a gutsy entry, but update-manager -d won't fetch a new copy, since the timestamp on the file is recent, so the upgrade button won't appear.