* apt-pkg/algorithms.cc:

  - Do not propagate negative scores from rdepends. Propagating the absolute
    value of a negative score may boost obsolete packages and keep them
    installed instead of installing their successors.  (Closes: #699759)

apt-pkg/algorithms.cc

@@ -645,7 +645,10 @@ void pkgProblemResolver::MakeScores()
 	      D->Type != pkgCache::Dep::Recommends))
 	    continue;	 
 	 
-	 Scores[I->ID] += abs(OldScores[D.ParentPkg()->ID]);
+	 // Do not propagate negative scores otherwise
+	 // an extra (-2) package might score better than an optional (-1)
+	 if (OldScores[D.ParentPkg()->ID] > 0)
+	     Scores[I->ID] += OldScores[D.ParentPkg()->ID];
       }      
    }
 

debian/changelog

@@ -4,7 +4,13 @@ apt (0.9.7.9) UNRELEASED; urgency=low
   * properly handle if-modfied-since with libcurl/https 
     (closes: #705648)
   
- -- Michael Vogt <michael.vogt@ubuntu.com>  Wed, 08 May 2013 16:20:13 +0200
+  [ Andreas Beckman ]
+  * apt-pkg/algorithms.cc:
+    - Do not propagate negative scores from rdepends. Propagating the absolute
+      value of a negative score may boost obsolete packages and keep them
+      installed instead of installing their successors.  (Closes: #699759)
+  
+ -- Michael Vogt <mvo@debian.org>  Wed, 08 May 2013 17:46:10 +0200
 
 apt (0.9.7.8) unstable; urgency=criticial