Slow completion when using aptitude

[cheer_xiao <xiaqqaix@xxxxxxxxx>]

Hi zsh users and hackers,
I'm running Ubuntu 10.04 on my box. I have found that tab-completion
for package names is slow when I use aptitude; however when I try
apt-get instead, the completion is almost instinct. I Google-ed and
found out that zsh switches to apt-cache policy for package name
completion some years ago, due to slow completion. I suspect that that
switch didn't take aptitude into concern, and it shouldn't be hard to
fix. Anyone willing to look into this? I'm using the version from git
repo.

And another small related issue: the command tab-completion of zsh
doesn't seem to know aptitude build-dep, which has been around for a
few years but (unfortunately) undocumented. The bash that comes with
Ubuntu knows this.