solver3: Try candidate before installed version on upgrade

This fixes --no-strict-pinning attempting to upgrade all the versions
on the system. Adjust the upgrade test case accordingly:

1) no-strict-pinning pulls in systemd despite it being pinned down due
   to a dependenc (this was true before this fix)
2) no-strict-pinning does not pull in the upgrade-simple because nothing
   depends on it (this is what the test fixes)

2 files changed, 60 insertions, 2 deletions

diff --git a/apt-pkg/solver3.cc b/apt-pkg/solver3.cc
index ab66c9501..58fb07c01 100644
--- a/apt-pkg/solver3.cc
+++ b/apt-pkg/solver3.cc
@@ -46,8 +46,15 @@ struct CompareProviders3 /*{{{*/
       {
 	 if (AV == BV)
 	    return false;
-	 if (not upgrade && A->CurrentVer != 0 && A.CurrentVer() == AV)
-	    return true;
+	 // The current version should win, unless we are upgrading and the other is the
+	 // candidate.
+	 // If AV is the current version, AV only wins on upgrades if BV is not the candidate.
+	 if (A.CurrentVer() == AV)
+	    return upgrade ? Policy.GetCandidateVer(A) != BV : true;
+	 // If BV is the current version, AV only wins on upgrades if it is the candidate.
+	 if (A.CurrentVer() == BV)
+	    return upgrade ? Policy.GetCandidateVer(A) == AV : false;
+	 // If neither are the current version, order them by priority.
 	 if (Policy.GetPriority(AV) < Policy.GetPriority(BV))
 	    return false;
 
diff --git a/test/integration/test-apt-get-upgrade b/test/integration/test-apt-get-upgrade
index 9fb2b41d1..c9e56d97d 100755
--- a/test/integration/test-apt-get-upgrade
+++ b/test/integration/test-apt-get-upgrade
@@ -167,3 +167,54 @@ Conf upgrade-with-conflict (2.0 unstable [all])
 Conf new-dep (1.0 stable [all])
 Conf upgrade-simple (2.0 unstable [all])
 Conf upgrade-with-new-dep (2.0 unstable [all])' aptget -s dist-upgrade
+
+# --no-strict-pinning pulls in systemd due to the dependency
+testsuccessequal 'Reading package lists...
+Building dependency tree...
+Calculating upgrade...
+The following packages will be REMOVED:
+  conflicting-dep
+The following NEW packages will be installed:
+  new-dep systemd
+The following packages will be upgraded:
+  init upgrade-simple upgrade-with-conflict upgrade-with-new-dep
+4 upgraded, 2 newly installed, 1 to remove and 0 not upgraded.
+Remv conflicting-dep [1.0]
+Inst systemd (2 unstable [all])
+Conf systemd (2 unstable [all])
+Inst init [1] (2 unstable [all])
+Inst upgrade-with-conflict [1.0] (2.0 unstable [all])
+Inst new-dep (1.0 stable [all])
+Inst upgrade-simple [1.0] (2.0 unstable [all])
+Inst upgrade-with-new-dep [1.0] (2.0 unstable [all])
+Conf init (2 unstable [all])
+Conf upgrade-with-conflict (2.0 unstable [all])
+Conf new-dep (1.0 stable [all])
+Conf upgrade-simple (2.0 unstable [all])
+Conf upgrade-with-new-dep (2.0 unstable [all])' aptget -s dist-upgrade --no-strict-pinning --solver 3.0
+
+# --no-strict-pinning does not cause a package to be upgraded on its own, though.
+echo 'Package: upgrade-simple
+Pin: release unstable
+Pin-Priority: -1' > rootdir/etc/apt/preferences.d/no-strict-pinning.pref
+testsuccessequal 'Reading package lists...
+Building dependency tree...
+Calculating upgrade...
+The following packages will be REMOVED:
+  conflicting-dep
+The following NEW packages will be installed:
+  new-dep systemd
+The following packages will be upgraded:
+  init upgrade-with-conflict upgrade-with-new-dep
+3 upgraded, 2 newly installed, 1 to remove and 0 not upgraded.
+Remv conflicting-dep [1.0]
+Inst systemd (2 unstable [all])
+Conf systemd (2 unstable [all])
+Inst init [1] (2 unstable [all])
+Inst upgrade-with-conflict [1.0] (2.0 unstable [all])
+Inst new-dep (1.0 stable [all])
+Inst upgrade-with-new-dep [1.0] (2.0 unstable [all])
+Conf init (2 unstable [all])
+Conf upgrade-with-conflict (2.0 unstable [all])
+Conf new-dep (1.0 stable [all])
+Conf upgrade-with-new-dep (2.0 unstable [all])' aptget -s dist-upgrade --no-strict-pinning --solver 3.0