Use initial metadata in P2DependencyTreeGenerator

Currently P2DependencyTreeGenerator computes the "inital" units using
the InstallableUnitGenerator, but that data is actually already
available from the INITAL dependency metadata.

(cherry picked from commit 5d13ab0)

tycho-core/src/main/java/org/eclipse/tycho/p2/tools/P2DependencyTreeGenerator.java

@@ -14,6 +14,7 @@
 package org.eclipse.tycho.p2.tools;
 
 import java.util.ArrayList;
+import java.util.Collection;
 import java.util.Collections;
 import java.util.Comparator;
 import java.util.HashMap;
@@ -36,10 +37,11 @@
 import org.eclipse.equinox.p2.metadata.IInstallableUnit;
 import org.eclipse.equinox.p2.metadata.IRequirement;
 import org.eclipse.tycho.ArtifactDescriptor;
+import org.eclipse.tycho.IDependencyMetadata.DependencyMetadataType;
+import org.eclipse.tycho.ReactorProject;
 import org.eclipse.tycho.core.TychoProject;
 import org.eclipse.tycho.core.TychoProjectManager;
 import org.eclipse.tycho.core.osgitools.DefaultReactorProject;
-import org.eclipse.tycho.p2maven.InstallableUnitGenerator;
 
 /**
  * Utility class for converting a flat dependency into a dependency tree. The tree is structured in
@@ -52,14 +54,11 @@
  */
 @Component(role = P2DependencyTreeGenerator.class)
 public final class P2DependencyTreeGenerator {
-    private final InstallableUnitGenerator generator;
     private final TychoProjectManager projectManager;
     private final LegacySupport legacySupport;
 
     @Inject
-    public P2DependencyTreeGenerator(InstallableUnitGenerator generator, TychoProjectManager projectManager,
-            LegacySupport legacySupport) {
-        this.generator = generator;
+    public P2DependencyTreeGenerator(TychoProjectManager projectManager, LegacySupport legacySupport) {
         this.projectManager = projectManager;
         this.legacySupport = legacySupport;
     }
@@ -73,7 +72,7 @@ public P2DependencyTreeGenerator(InstallableUnitGenerator generator, TychoProjec
      *            One of the Maven projects of the current reactor build. If this project is not a
      *            Tycho project (e.g. the parent pom), an empty list is returned.
      * @param unmapped
-     *            A set containing all IUs which could not be added to the dependency tree.Meaning
+     *            A set containing all IUs which could not be added to the dependency tree. Meaning
      *            that those units are required by the project but not by any of its IUs. Must be
      *            mutable.
      * @return as described.
@@ -88,14 +87,14 @@ public List<DependencyTreeNode> buildDependencyTree(MavenProject project, Set<II
             return Collections.emptyList();
         }
 
+        ReactorProject reactorProject = DefaultReactorProject.adapt(project);
         List<ArtifactDescriptor> artifacts = tychoProject.get() //
-                .getDependencyArtifacts(DefaultReactorProject.adapt(project)) //
+                .getDependencyArtifacts(reactorProject) //
                 .getArtifacts();
         Set<IInstallableUnit> units = artifacts.stream() //
                 .flatMap(d -> d.getInstallableUnits().stream()) //
                 .collect(Collectors.toCollection(HashSet::new));
-        List<IInstallableUnit> initial = List
-                .copyOf(generator.getInstallableUnits(project, legacySupport.getSession(), false));
+        Set<IInstallableUnit> initial = reactorProject.getDependencyMetadata(DependencyMetadataType.INITIAL);
         units.removeAll(initial);
 
         return Collections.unmodifiableList(DependencyTreeNode.create(initial, units, unmapped));
@@ -156,14 +155,14 @@ public String toString() {
          * @return A list of dependency tree models. Each model in this list matches an IU of
          *         {@code initial}.
          */
-        private static List<DependencyTreeNode> create(List<IInstallableUnit> initial, Set<IInstallableUnit> units,
-                Set<IInstallableUnit> unmapped) {
+        private static List<DependencyTreeNode> create(Collection<IInstallableUnit> initial,
+                Set<IInstallableUnit> units, Set<IInstallableUnit> unmapped) {
             List<DependencyTreeNode> rootNodes = new ArrayList<>();
-            for (int i = 0; i < initial.size(); ++i) {
-                DependencyTreeNode rootNode = new DependencyTreeNode(initial.get(i), null);
+            initial.stream().sorted(COMPARATOR).forEach(iu -> {
+                DependencyTreeNode rootNode = new DependencyTreeNode(iu, null);
                 create(rootNode, units);
                 rootNodes.add(rootNode);
-            }
+            });
             unmapped.addAll(units);
             return rootNodes;
         }