Bug 126616 IStorageMerger is not called in three-way merge with no common ancestor
I20060131-1200 IMergeContext.merge(IDiff[], boolean, IProgressMonitor) does not attempt to automerge two revisions if no common ancestor is available. Depending on the file content, no common ancestor is needed for automerging (e.g refactoring history files, where merging is simple the union operation). I suggest to call the corresponding IStorageMerger with an empty stream in this case, or have a predicate which tells whether the merger supports three-way merging with no common ancestor.
org.eclipse.ltk.ui.refactoring/src/org/eclipse/ltk/internal/ui/refactoring/model/RefactoringIndexMerger.java
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.UnsupportedEncodingException;
import java.util.Arrays;
import java.util.Comparator;
import java.util.HashSet;
import java.util.Set;
import org.eclipse.team.core.mapping.IStorageMerger;
import org.eclipse.core.runtime.CoreException;
import org.eclipse.core.runtime.IProgressMonitor;
import org.eclipse.core.runtime.IStatus;
import org.eclipse.core.runtime.Status;
import org.eclipse.core.resources.IStorage;
import org.eclipse.ltk.core.refactoring.RefactoringDescriptor;
import org.eclipse.ltk.core.refactoring.RefactoringDescriptorProxy;
import org.eclipse.ltk.internal.core.refactoring.history.RefactoringHistoryManager;
import org.eclipse.ltk.internal.ui.refactoring.RefactoringUIMessages;
import org.eclipse.ltk.internal.ui.refactoring.RefactoringUIPlugin;
import org.eclipse.compare.IStreamMerger;
/**
 * Combined storage and tream merger for refactoring history index files.
 * 
 * @since 3.2
 */
public final class RefactoringIndexMerger implements IStreamMerger, IStorageMerger {
	/**
	 * Creates a new refactoring index merger.
	 */
	public RefactoringIndexMerger() {