ThreeWayMerger.java

/*
 * Copyright (C) 2009, Google Inc.
 * Copyright (C) 2012, Research In Motion Limited 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.errors.IncorrectObjectTypeException;
import org.eclipse.jgit.errors.MissingObjectException;
import org.eclipse.jgit.lib.AnyObjectId;
import org.eclipse.jgit.lib.ObjectId;
import org.eclipse.jgit.lib.ObjectInserter;
import org.eclipse.jgit.lib.Repository;
import org.eclipse.jgit.revwalk.RevCommit;
import org.eclipse.jgit.revwalk.RevTree;
import org.eclipse.jgit.treewalk.AbstractTreeIterator;
import org.eclipse.jgit.treewalk.EmptyTreeIterator;

/**
 * A merge of 2 trees, using a common base ancestor tree.
 */
public abstract class ThreeWayMerger extends Merger {
    private RevTree baseTree;

    private ObjectId baseCommitId;

    /**
     * Create a new merge instance for a repository.
     *
     * @param local
     *            the repository this merger will read and write data on.
     */
    protected ThreeWayMerger(Repository local) {
        super(local);
    }

    /**
     * Create a new merge instance for a repository.
     *
     * @param local
     *            the repository this merger will read and write data on.
     * @param inCore
     *            perform the merge in core with no working folder involved
     */
    protected ThreeWayMerger(Repository local, boolean inCore) {
        this(local);
    }

    /**
     * Create a new in-core merge instance from an inserter.
     *
     * @param inserter
     *            the inserter to write objects to.
     * @since 4.8
     */
    protected ThreeWayMerger(ObjectInserter inserter) {
        super(inserter);
    }

    /**
     * Set the common ancestor tree.
     *
     * @param id
     *            common base treeish; null to automatically compute the common
     *            base from the input commits during
     *            {@link #merge(AnyObjectId...)}.
     * @throws org.eclipse.jgit.errors.IncorrectObjectTypeException
     *             the object is not a treeish.
     * @throws org.eclipse.jgit.errors.MissingObjectException
     *             the object does not exist.
     * @throws java.io.IOException
     *             the object could not be read.
     */
    public void setBase(AnyObjectId id) throws MissingObjectException,
            IncorrectObjectTypeException, IOException {
        if (id != null) {
            baseTree = walk.parseTree(id);
        } else {
            baseTree = null;
        }
    }

    /** {@inheritDoc} */
    @Override
    public boolean merge(AnyObjectId... tips) throws IOException {
        if (tips.length != 2)
            return false;
        return super.merge(tips);
    }

    /** {@inheritDoc} */
    @Override
    public ObjectId getBaseCommitId() {
        return baseCommitId;
    }

    /**
     * Create an iterator to walk the merge base.
     *
     * @return an iterator over the caller-specified merge base, or the natural
     *         merge base of the two input commits.
     * @throws java.io.IOException
     */
    protected AbstractTreeIterator mergeBase() throws IOException {
        if (baseTree != null) {
            return openTree(baseTree);
        }
        RevCommit baseCommit = (baseCommitId != null) ? walk
                .parseCommit(baseCommitId) : getBaseCommit(sourceCommits[0],
                sourceCommits[1]);
        if (baseCommit == null) {
            baseCommitId = null;
            return new EmptyTreeIterator();
        }
        baseCommitId = baseCommit.toObjectId();
        return openTree(baseCommit.getTree());
    }
}