Enable referenced repositories when resolving the target content

Currently referenced repositories are ignored, that prevents sharing of
items that are already available in the referenced repository.

This enables searching references (if possible) to find IUs and
dependencies in these referenced repositories as well.

Fix #720

ui/org.eclipse.pde.core/src/org/eclipse/pde/internal/core/target/P2TargetUtils.java

@@ -25,6 +25,7 @@
 import java.util.HashMap;
 import java.util.HashSet;
 import java.util.Iterator;
+import java.util.LinkedHashSet;
 import java.util.List;
 import java.util.Map;
 import java.util.Set;
@@ -1008,14 +1009,17 @@ static IQueryable<IInstallableUnit> getQueryableMetadata(URI[] repos, IProgressM
 		}
 
 		int repoCount = repos.length;
-		SubMonitor subMonitor = SubMonitor.convert(monitor, repoCount);
-
+		SubMonitor subMonitor = SubMonitor.convert(monitor, repoCount * 2);
 
+		Set<IRepositoryReference> seen = new HashSet<>();
 		List<IMetadataRepository> result = new ArrayList<>(repoCount);
+		List<IMetadataRepository> additional = new ArrayList<>();
 		MultiStatus repoStatus = new MultiStatus(PDECore.PLUGIN_ID, 0, Messages.IUBundleContainer_ProblemsLoadingRepositories, null);
 		for (int i = 0; i < repoCount; ++i) {
 			try {
-				result.add(manager.loadRepository(repos[i], subMonitor.split(1)));
+				IMetadataRepository repository = manager.loadRepository(repos[i], subMonitor.split(1));
+				result.add(repository);
+				addReferences(repository, additional, seen, manager, subMonitor.split(1));
 			} catch (ProvisionException e) {
 				repoStatus.add(e.getStatus());
 			}
@@ -1024,10 +1028,31 @@ static IQueryable<IInstallableUnit> getQueryableMetadata(URI[] repos, IProgressM
 		if (result.size() != repos.length) {
 			throw new CoreException(repoStatus);
 		}
+		result.addAll(additional);
 		if (result.size() == 1) {
 			return result.get(0);
 		}
-		return QueryUtil.compoundQueryable(result);
+		return QueryUtil.compoundQueryable(new LinkedHashSet<>(result));
+	}
+
+	private static void addReferences(IMetadataRepository repository, List<IMetadataRepository> result,
+			Set<IRepositoryReference> seen, IMetadataRepositoryManager manager, IProgressMonitor monitor) {
+		Collection<IRepositoryReference> references = repository.getReferences();
+		SubMonitor subMonitor = SubMonitor.convert(monitor, references.size() * 2);
+		for (IRepositoryReference reference : references) {
+			if (reference.getType() == IRepository.TYPE_METADATA && seen.add(reference)) {
+				try {
+					IMetadataRepository referencedRepository = manager.loadRepository(reference.getLocation(),
+							subMonitor.split(1));
+					result.add(referencedRepository);
+					addReferences(referencedRepository, result, seen, manager, subMonitor.split(1));
+				} catch (ProvisionException e) {
+					//if reference can't be loaded just ignore it here but log the error just in case the user wants to act on this
+					PDECore.log(e);
+				}
+			}
+		}
+
 	}
 
 	/**
@@ -1056,6 +1081,7 @@ private void resolveWithPlanner(ITargetDefinition target, IProgressMonitor monit
 		}
 
 		ProvisioningContext context = new ProvisioningContext(getAgent());
+		context.setProperty(ProvisioningContext.FOLLOW_REPOSITORY_REFERENCES, Boolean.toString(true));
 		context.setMetadataRepositories(getMetadataRepositories(target));
 		context.setArtifactRepositories(getArtifactRepositories(target));
 
@@ -1279,6 +1305,7 @@ private void resolveWithSlicer(ITargetDefinition target, IProgressMonitor monito
 		ProvisioningContext context = new ProvisioningContext(getAgent());
 		context.setMetadataRepositories(repositories);
 		context.setArtifactRepositories(getArtifactRepositories(target));
+		context.setProperty(ProvisioningContext.FOLLOW_REPOSITORY_REFERENCES, Boolean.toString(true));
 		IProvisioningPlan plan = engine.createPlan(fProfile, context);
 		setPlanProperties(plan, target, TargetDefinitionPersistenceHelper.MODE_SLICER);