update manager should cache changelog information by url

[lavinog]

Binary package hint: update-manager

Currently update-manager will download the same changelogs multiple times if there are multiple packages with the same changelog.

Example:
Today I started wireshark to capture packets.
Started update manager
The first package listed was apt and it downloaded the changelog automatically
wireshark caught this request:
48 8.591803 192.168.1.104 91.189.90.132 HTTP GET /changelogs/pool/main/a/apt/apt_0.7.25.3ubuntu9/NEWS.Debian HTTP/1.1
63 8.923160 192.168.1.104 91.189.90.132 HTTP GET /changelogs/pool/main/a/apt/apt_0.7.25.3ubuntu9/changelog HTTP/1.1

Then I selected the next package: apt-transport-https
wireshark reported:
95 13.335957 192.168.1.104 91.189.90.132 HTTP GET /changelogs/pool/main/a/apt/apt_0.7.25.3ubuntu9/NEWS.Debian HTTP/1.1
110 13.665300 192.168.1.104 91.189.90.132 HTTP GET /changelogs/pool/main/a/apt/apt_0.7.25.3ubuntu9/changelog HTTP/1.1

The next package: apt-utils
144 17.995672 192.168.1.104 91.189.90.132 HTTP GET /changelogs/pool/main/a/apt/apt_0.7.25.3ubuntu9/NEWS.Debian HTTP/1.1
159 18.331389 192.168.1.104 91.189.90.132 HTTP GET /changelogs/pool/main/a/apt/apt_0.7.25.3ubuntu9/changelog HTTP/1.1

This is a waste of bandwidth and server resources.
update-manager could cache each changelog in a dictionary by url key.
Doing this could greatly reduce the number of requests the changelog server receives.

ProblemType: Bug
DistroRelease: Ubuntu 10.04
Package: update-manager 1:0.134.8
ProcVersionSignature: Ubuntu 2.6.32-22.33-generic 2.6.32.11+drm33.2
Uname: Linux 2.6.32-22-generic i686
Architecture: i386
Date: Tue May 18 13:15:52 2010
InstallationMedia: Ubuntu 10.04 "Lucid Lynx" - Alpha i386 (20100312)
PackageArchitecture: all
ProcEnviron:
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SourcePackage: update-manager