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

@@ -1008,14 +1008,17 @@ 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());
 			}
@@ -1024,12 +1027,33 @@ 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);
 	}
 
+	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);
+				}
+			}
+		}
+
+	}
+
 	/**
 	 * Used to resolve the contents of this container if the user is including all required software.  The p2 planner is used
 	 * to determine the complete set of IUs required to run the selected software.  If all requirements are met, the bundles
@@ -1056,6 +1080,7 @@ 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));