* apt-pkg/depcache.cc:

  - prefer to install packages which have an already installed M-A:same
    sibling while choosing providers (LP: #1130419)

apt-pkg/depcache.cc

@@ -951,6 +951,37 @@ struct CompareProviders {
    {
       pkgCache::PkgIterator const A = AV.ParentPkg();
       pkgCache::PkgIterator const B = BV.ParentPkg();
+      // Prefer MA:same packages if other architectures for it are installed
+      if ((AV->MultiArch & pkgCache::Version::Same) == pkgCache::Version::Same ||
+	  (BV->MultiArch & pkgCache::Version::Same) == pkgCache::Version::Same)
+      {
+	 bool instA = false;
+	 if ((AV->MultiArch & pkgCache::Version::Same) == pkgCache::Version::Same)
+	 {
+	    pkgCache::GrpIterator Grp = A.Group();
+	    for (pkgCache::PkgIterator P = Grp.PackageList(); P.end() == false; P = Grp.NextPkg(P))
+	       if (P->CurrentVer != 0)
+	       {
+		  instA = true;
+		  break;
+	       }
+	 }
+	 bool instB = false;
+	 if ((BV->MultiArch & pkgCache::Version::Same) == pkgCache::Version::Same)
+	 {
+	    pkgCache::GrpIterator Grp = B.Group();
+	    for (pkgCache::PkgIterator P = Grp.PackageList(); P.end() == false; P = Grp.NextPkg(P))
+	    {
+	       if (P->CurrentVer != 0)
+	       {
+		  instB = true;
+		  break;
+	       }
+	    }
+	 }
+	 if (instA != instB)
+	    return instA == false;
+      }
       // Prefer packages in the same group as the target; e.g. foo:i386, foo:amd64
       if (A->Group != B->Group)
       {

debian/changelog

@@ -34,6 +34,11 @@ apt (0.9.7.8) UNRELEASED; urgency=low
   * apt-pkg/indexrecords.cc:
     - support '\r' in the Release file
 
+  [ David Kalnischkies ]
+  * apt-pkg/depcache.cc:
+    - prefer to install packages which have an already installed M-A:same
+      sibling while choosing providers (LP: #1130419)
+
  -- Christian Perrier <bubulle@debian.org>  Mon, 24 Dec 2012 07:01:20 +0100
 
 apt (0.9.7.7) unstable; urgency=low

test/integration/test-ubuntu-bug-1130419-prefer-installed-ma-same-siblings

@@ -0,0 +1,104 @@
+#!/bin/sh
+set -e
+
+TESTDIR=$(readlink -f $(dirname $0))
+. $TESTDIR/framework
+setupenvironment
+configarchitecture 'amd64' 'i386'
+
+insertpackage 'stable' 'libmesa' 'amd64,i386' '1' 'Multi-Arch: same'
+insertpackage 'stable' 'libmesa-lts' 'amd64,i386' '1' 'Provides: libmesa
+Conflicts: libmesa
+Multi-Arch: same'
+insertpackage 'stable' 'steam' 'i386' '1' 'Depends: libmesa'
+
+insertpackage 'unstable' 'libmesa' 'amd64,i386' '2' 'Multi-Arch: same'
+insertpackage 'unstable' 'libmesa-lts' 'amd64,i386' '2' 'Provides: libmesa
+Conflicts: libmesa
+Multi-Arch: same'
+insertpackage 'unstable' 'steam' 'i386' '2' 'Depends: libmesa'
+
+setupaptarchive
+
+testequal 'Reading package lists...
+Building dependency tree...
+The following extra packages will be installed:
+  libmesa:i386
+The following NEW packages will be installed:
+  libmesa:i386 steam:i386
+0 upgraded, 2 newly installed, 0 to remove and 0 not upgraded.
+Inst libmesa:i386 (1 stable [i386])
+Inst steam:i386 (1 stable [i386])
+Conf libmesa:i386 (1 stable [i386])
+Conf steam:i386 (1 stable [i386])' aptget install steam -st stable
+testequal 'Reading package lists...
+Building dependency tree...
+The following extra packages will be installed:
+  libmesa:i386
+The following NEW packages will be installed:
+  libmesa:i386 steam:i386
+0 upgraded, 2 newly installed, 0 to remove and 0 not upgraded.
+Inst libmesa:i386 (2 unstable [i386])
+Inst steam:i386 (2 unstable [i386])
+Conf libmesa:i386 (2 unstable [i386])
+Conf steam:i386 (2 unstable [i386])' aptget install steam -st unstable
+
+cp rootdir/var/lib/dpkg/status default-status.dpkg
+insertinstalledpackage 'libmesa' 'amd64' '1' 'Multi-Arch: same'
+testequal 'Reading package lists...
+Building dependency tree...
+The following extra packages will be installed:
+  libmesa:i386
+The following NEW packages will be installed:
+  libmesa:i386 steam:i386
+0 upgraded, 2 newly installed, 0 to remove and 0 not upgraded.
+Inst libmesa:i386 (1 stable [i386])
+Inst steam:i386 (1 stable [i386])
+Conf libmesa:i386 (1 stable [i386])
+Conf steam:i386 (1 stable [i386])' aptget install steam -st stable
+testequal 'Reading package lists...
+Building dependency tree...
+The following extra packages will be installed:
+  libmesa libmesa:i386
+The following NEW packages will be installed:
+  libmesa:i386 steam:i386
+The following packages will be upgraded:
+  libmesa
+1 upgraded, 2 newly installed, 0 to remove and 0 not upgraded.
+Inst libmesa [1] (2 unstable [amd64])
+Inst libmesa:i386 (2 unstable [i386])
+Inst steam:i386 (2 unstable [i386])
+Conf libmesa (2 unstable [amd64])
+Conf libmesa:i386 (2 unstable [i386])
+Conf steam:i386 (2 unstable [i386])' aptget install steam -st unstable
+
+cp default-status.dpkg rootdir/var/lib/dpkg/status
+insertinstalledpackage 'libmesa-lts' 'amd64' '1' 'Provides: libmesa
+Conflicts: libmesa
+Multi-Arch: same'
+testequal 'Reading package lists...
+Building dependency tree...
+The following extra packages will be installed:
+  libmesa-lts:i386
+The following NEW packages will be installed:
+  libmesa-lts:i386 steam:i386
+0 upgraded, 2 newly installed, 0 to remove and 0 not upgraded.
+Inst libmesa-lts:i386 (1 stable [i386])
+Inst steam:i386 (1 stable [i386])
+Conf libmesa-lts:i386 (1 stable [i386])
+Conf steam:i386 (1 stable [i386])' aptget install steam -st stable
+testequal 'Reading package lists...
+Building dependency tree...
+The following extra packages will be installed:
+  libmesa-lts libmesa-lts:i386
+The following NEW packages will be installed:
+  libmesa-lts:i386 steam:i386
+The following packages will be upgraded:
+  libmesa-lts
+1 upgraded, 2 newly installed, 0 to remove and 0 not upgraded.
+Inst libmesa-lts [1] (2 unstable [amd64])
+Inst libmesa-lts:i386 (2 unstable [i386])
+Inst steam:i386 (2 unstable [i386])
+Conf libmesa-lts (2 unstable [amd64])
+Conf libmesa-lts:i386 (2 unstable [i386])
+Conf steam:i386 (2 unstable [i386])' aptget install steam -st unstable