Same version, different package issue..

[Jason Gunthorpe <jgg@ualberta.ca>]

I have checked in a fairly simple fix that deals with bug #30237 and the
broader issue of having multiple different packages with the same version
number. (such as super has..)

What I do is compute a digest for some crucial fields using CRC-16. This
creates a Package, Version, Digest triplet that should uniquely represent
this package. It is still possible to trick it if you either collide the
hash or create two packages with identical fields that are still
different.

When it does detect a difference it orders them backwards by occurance, so
the status file will be listed last. This means that APT will always try
to upgrade a locally compiled version with the archive version 
(via a hold or something) and assuming the archive lists the package
sources in order of newness it will try to upgrade to the newest source.

The fields deemed important are Installed-Size, Depends, Pre-Depends,
Suggests, Recommends, Conflicts, and Replaces. And it looks something
like:

Wakko{root}~/work/apt/build/bin#./apt-cache showpkg super
Package: super
Versions:
3.12.1-1(/var/state/apt/lists/http.us.debian.org_debian_dists_potato_main_binary-i386_Packages),
3.12.1-1(/var/state/apt/lists/http.us.debian.org_debian_dists_slink_main_binary-i386_Packages),
Reverse Depends: 

This is another soname bump though..

Jason