Ordering

[Jason Gunthorpe <jgg@gpu.srv.ualberta.ca>]

I think I have solved a majority of the problems with ordering, my biggest
fear is that the limited interface to dpkg is going to make a mess of
everything (imagine, tell it to do something, it fails, you have no idea 
what failed..) :< There are likely problems with conflict+replace
packages too.. 

Here is the blurb on the ordering code,

   This is a modified version of Manoj's Routine B. It consists of two
   independant stages, installation+removal ordering and configuration
   ordering.

   Installation ordering considers each package and its predepends+conflicts
   only. It orders the packages so that when a package is unpacked there
   are no unmet predepends or conflicts.

   Removal ordering considers each package and its reverse dependancies
   and reverse predepends. It shceduals and unpack of its reverses before
   it is removed to advoid broken configured dependancies. Removal and
   installation happen in the same pass so packages can be unpacked to
   clear removal depends requirements.

   Configuration ordering considers each package that has been unpacked
   and decides if it is possible to configure it. Because ordered removals
   are involved it is possible a package was unpacked to satisify a remove
   but does not have complete dependancies yet. These packages are ignored
   in the configure ordering phase. Once a list of valid, configurable
   packages has been gathered it then sorts by dependancy only to produce
   an ordered configure list.

   By calling the configuration routine whenever an unmet predepends is
   encountered breaks in the installation are created. The configuration
   routine installs all the packages it can, though only the packages
   required to deal with predepends are truely needed.

Jason