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/RefactoringHistoryMerger.java
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 * Copyright (c) 2005 IBM Corporation and others.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
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 * Contributors:
 *     IBM Corporation - initial API and implementation
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package org.eclipse.ltk.internal.ui.refactoring.model;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
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;