Improve new package/file notification protocol

[fpletz]

currently triggering refetch of complete package list on addition of new file (through inotify) -> traffic-intensive

possible solutions:

• send out msgs like "I got xxx_1.0-1_all.deb now, please add to my pkg list"
• accumulate new packages and trigger either package list updates or above msgs (announcing all new pkgs per msg) on completion of fetching through APT

[fpletz]

Basic queuing of events is in 0.3, deferring further optimization to 0.4.

[Andrew McCarthy]

Instead of retrieving a package list immediately when notified, the client could instead mark the list as out-of-date. It would then only need to update these out-of-date lists when it receives a request for a package file from localhost, which for production machines might only be once a day.

To avoid a sudden large burst of updates, the client might choose to update the lists when more than 10 (for example) are out-of-date.