StrategyOneSided.java

/*
 * Copyright (C) 2008-2009, Google Inc.
 * Copyright (C) 2009, Robin Rosenberg <robin.rosenberg@dewire.com> and others
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Distribution License v. 1.0 which is available at
 * https://www.eclipse.org/org/documents/edl-v10.php.
 *
 * SPDX-License-Identifier: BSD-3-Clause
 */

package org.eclipse.jgit.merge;

import java.io.IOException;

import org.eclipse.jgit.lib.Config;
import org.eclipse.jgit.lib.ObjectId;
import org.eclipse.jgit.lib.ObjectInserter;
import org.eclipse.jgit.lib.Repository;

/**
 * Trivial merge strategy to make the resulting tree exactly match an input.
 * <p>
 * This strategy can be used to cauterize an entire side branch of history, by
 * setting the output tree to one of the inputs, and ignoring any of the paths
 * of the other inputs.
 */
public class StrategyOneSided extends MergeStrategy {
    private final String strategyName;

    private final int treeIndex;

    /**
     * Create a new merge strategy to select a specific input tree.
     *
     * @param name
     *            name of this strategy.
     * @param index
     *            the position of the input tree to accept as the result.
     */
    protected StrategyOneSided(String name, int index) {
        strategyName = name;
        treeIndex = index;
    }

    /** {@inheritDoc} */
    @Override
    public String getName() {
        return strategyName;
    }

    /** {@inheritDoc} */
    @Override
    public Merger newMerger(Repository db) {
        return new OneSide(db, treeIndex);
    }

    /** {@inheritDoc} */
    @Override
    public Merger newMerger(Repository db, boolean inCore) {
        return new OneSide(db, treeIndex);
    }

    /** {@inheritDoc} */
    @Override
    public Merger newMerger(ObjectInserter inserter, Config config) {
        return new OneSide(inserter, treeIndex);
    }

    static class OneSide extends Merger {
        private final int treeIndex;

        protected OneSide(Repository local, int index) {
            super(local);
            treeIndex = index;
        }

        protected OneSide(ObjectInserter inserter, int index) {
            super(inserter);
            treeIndex = index;
        }

        @Override
        protected boolean mergeImpl() throws IOException {
            return treeIndex < sourceTrees.length;
        }

        @Override
        public ObjectId getResultTreeId() {
            return sourceTrees[treeIndex];
        }

        @Override
        public ObjectId getBaseCommitId() {
            return null;
        }
    }
}