Some questions on apt-pkg

[Daniel Burrows <Daniel_Burrows@brown.edu>]

  Hello all,

  I'm trying to learn how to use libapt-pkg.  So far the combination of the
documentation, the header files, the source, and the source of other programs
that use it has been enough, but I've come across some questions that I can't
work out from these..at least not quickly enough to make it easier than bugging
you folks :)

  Here's what I'd like to know (two things):

  -> pkgDepCache::MarkInstall appears to automatically and recursively install
   dependencies if AutoInst is set to true.  Is there any way to find out what
   it has done?  That is, I'd like to get a list of packages whose state has
   magically changed.  I suppose I could just keep my own copy of each package's
   status, but that seems a little..erm..ugly.
     Also, if the user tries to do something that's not possible or where a
   choice can be made, how can I find out?  (eg, where one of several packages
   can be installed to fulfill a dependency)  Or is this Not Relevant?  (as
   I wrote this question I thought of a [perhaps] better way to handle this than
   what I was thinking :) )

  -> What exactly does the Soft argument to pkgDepCache::MarkKeep do?

  -> How can I change the `target version' and/or `target dist' of a package?  I
   see lots of different ways to query it, but no way to modify it (eg, so the
   user can say "downgrade this package to an older version").

  I think that's it for now.

  Daniel

-- 
THERE IS NO HOPE BUT US.  THERE IS NO JUSTICE BUT US.  ALL THAT IS, IS OURS.
BUT WE MUST CARE.  FOR IF WE DO NOT CARE, THEN WE DO NOT EXIST...
     -- Terry Pratchett, _Reaper Man_