Ensure that for each all package at least one pseudopackage is installed

Removing pseudo packages is cool so far, the problem is that we will
remove with the not required removing so many pseudo packages that
we will have after the remove a few packages with NO installed pseudo
package (e.g. metapackages are good candidates) - so we will walk over
all these packages and try to find a pseudopackage for this package
we can install without breaking something.

apt-pkg/depcache.cc

@@ -634,10 +634,8 @@ bool pkgDepCache::RemovePseudoInstalledPkg(PkgIterator &Pkg, std::set<unsigned l
    if (strcmp(Pkg.Arch(),"all") == 0)
       return false;
 
-// std::cout << "CHECK " << Pkg << std::endl;
-
-   unsigned char const DepState = VersionState(V.DependsList(),DepInstall,DepInstMin,DepInstPolicy);
-   if ((DepState & DepInstMin) == DepInstMin) {
+   unsigned char const CurDepState = VersionState(V.DependsList(),DepInstall,DepInstMin,DepInstPolicy);
+   if ((CurDepState & DepInstMin) == DepInstMin) {
       // okay, the package isn't broken, but is the package also required?
       // If it has no real dependencies, no installed rdepends and doesn't
       // provide something of value, we will kill it as not required.
@@ -645,16 +643,15 @@ bool pkgDepCache::RemovePseudoInstalledPkg(PkgIterator &Pkg, std::set<unsigned l
       // a new dependency in a newer version…
       for (pkgCache::DepIterator D = V.DependsList();
 	   D.end() != true; ++D)
-	 if ((D->Type == pkgCache::Dep::Depends ||
-	      D->Type == pkgCache::Dep::PreDepends) &&
-	     D.ParentPkg()->Group != Pkg->Group)
+	 if (D.IsCritical() == true && D.ParentPkg()->Group != Pkg->Group)
 	    return false;
       for (DepIterator D = Pkg.RevDependsList(); D.end() != true; ++D)
       {
-	 if (D->Type != pkgCache::Dep::Depends &&
-	     D->Type != pkgCache::Dep::PreDepends)
+	 if (D.IsCritical() == false)
 	    continue;
 	 PkgIterator const P = D.ParentPkg();
+	 if (P->Group == Pkg->Group)
+	    continue;
 	 if (P->CurrentVer != 0)
 	    return false;
       }
@@ -800,6 +797,68 @@ void pkgDepCache::Update(OpProgress *Prog)
 	 }
 	 recheck.erase(p);
       }
+
+      /* Okay, we have killed a great amount of pseudopackages -
+	 we have killed so many that we have now arch "all" packages
+	 without an installed pseudo package, but we NEED an installed
+	 pseudo package, so we will search now for a pseudo package
+	 we can install without breaking everything. */
+      for (GrpIterator G = Cache->GrpBegin(); G.end() != true; ++G)
+      {
+	 PkgIterator P = G.FindPkg("all");
+	 if (P.end() == true)
+	    continue;
+	 if (P->CurrentVer == 0)
+	    continue;
+	 bool installed = false;
+	 for (P = G.FindPkg("any"); P.end() != true; P = G.NextPkg(P))
+	 {
+	    if (strcmp(P.Arch(), "all") == 0)
+	       continue;
+	    if (P->CurrentVer == 0)
+	       continue;
+	    installed = true;
+	    break;
+	 }
+	 if (installed == false)
+	    recheck.insert(G.Index());
+      }
+      std::vector<std::string> Archs = APT::Configuration::getArchitectures();
+      bool checkChanged = false;
+      do {
+	 for(std::set<unsigned long>::const_iterator g = recheck.begin();
+	     g != recheck.end(); ++g) {
+	    GrpIterator G = GrpIterator(*Cache, Cache->GrpP + *g);
+	    VerIterator allV = G.FindPkg("all").CurrentVer();
+	    for (std::vector<std::string>::const_iterator a = Archs.begin();
+		 a != Archs.end(); ++a)
+	    {
+	       PkgIterator P = G.FindPkg(*a);
+	       if (P.end() == true) continue;
+	       for (VerIterator V = P.VersionList(); V.end() != true; ++V)
+	       {
+		  // FIXME: String comparison isn't a save indicator!
+		  if (strcmp(allV.VerStr(),V.VerStr()) != 0)
+		     continue;
+		  unsigned char const CurDepState = VersionState(V.DependsList(),DepInstall,DepInstMin,DepInstPolicy);
+		  if ((CurDepState & DepInstMin) != DepInstMin)
+		     break; // we found the correct version, but it is broken. Better try another arch or later again
+		  P->CurrentVer = V.Index();
+		  AddStates(P);
+		  Update(P);
+		  AddSizes(P);
+		  checkChanged = true;
+		  break;
+	       }
+	    }
+	    recheck.erase(g);
+	 }
+      } while (checkChanged == true && recheck.empty() == false);
+
+      if (_config->FindB("Debug::MultiArchKiller", false) == true)
+	 for(std::set<unsigned long>::const_iterator g = recheck.begin();
+	     g != recheck.end(); ++g)
+	    std::cout << "No pseudo package for »" << GrpIterator(*Cache, Cache->GrpP + *g).Name() << "« installed" << std::endl;
    }
 
    if (Prog != 0)