StrategySimpleTwoWayInCore.java

/*
 * Copyright (C) 2008-2009, Google Inc. 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.dircache.DirCache;
import org.eclipse.jgit.dircache.DirCacheBuilder;
import org.eclipse.jgit.dircache.DirCacheEntry;
import org.eclipse.jgit.errors.UnmergedPathException;
import org.eclipse.jgit.lib.Config;
import org.eclipse.jgit.lib.FileMode;
import org.eclipse.jgit.lib.ObjectId;
import org.eclipse.jgit.lib.ObjectInserter;
import org.eclipse.jgit.lib.Repository;
import org.eclipse.jgit.treewalk.AbstractTreeIterator;
import org.eclipse.jgit.treewalk.NameConflictTreeWalk;

/**
 * Merges two commits together in-memory, ignoring any working directory.
 * <p>
 * The strategy chooses a path from one of the two input trees if the path is
 * unchanged in the other relative to their common merge base tree. This is a
 * trivial 3-way merge (at the file path level only).
 * <p>
 * Modifications of the same file path (content and/or file mode) by both input
 * trees will cause a merge conflict, as this strategy does not attempt to merge
 * file contents.
 */
public class StrategySimpleTwoWayInCore extends ThreeWayMergeStrategy {
    /**
     * Create a new instance of the strategy.
     */
    protected StrategySimpleTwoWayInCore() {
        //
    }

    /** {@inheritDoc} */
    @Override
    public String getName() {
        return "simple-two-way-in-core"; //$NON-NLS-1$
    }

    /** {@inheritDoc} */
    @Override
    public ThreeWayMerger newMerger(Repository db) {
        return new InCoreMerger(db);
    }

    /** {@inheritDoc} */
    @Override
    public ThreeWayMerger newMerger(Repository db, boolean inCore) {
        // This class is always inCore, so ignore the parameter
        return newMerger(db);
    }

    /** {@inheritDoc} */
    @Override
    public ThreeWayMerger newMerger(ObjectInserter inserter, Config config) {
        return new InCoreMerger(inserter);
    }

    private static class InCoreMerger extends ThreeWayMerger {
        private static final int T_BASE = 0;

        private static final int T_OURS = 1;

        private static final int T_THEIRS = 2;

        private final NameConflictTreeWalk tw;

        private final DirCache cache;

        private DirCacheBuilder builder;

        private ObjectId resultTree;

        InCoreMerger(Repository local) {
            super(local);
            tw = new NameConflictTreeWalk(local, reader);
            cache = DirCache.newInCore();
        }

        InCoreMerger(ObjectInserter inserter) {
            super(inserter);
            tw = new NameConflictTreeWalk(null, reader);
            cache = DirCache.newInCore();
        }

        @Override
        protected boolean mergeImpl() throws IOException {
            tw.addTree(mergeBase());
            tw.addTree(sourceTrees[0]);
            tw.addTree(sourceTrees[1]);

            boolean hasConflict = false;
            builder = cache.builder();
            while (tw.next()) {
                final int modeO = tw.getRawMode(T_OURS);
                final int modeT = tw.getRawMode(T_THEIRS);
                if (modeO == modeT && tw.idEqual(T_OURS, T_THEIRS)) {
                    add(T_OURS, DirCacheEntry.STAGE_0);
                    continue;
                }

                final int modeB = tw.getRawMode(T_BASE);
                if (modeB == modeO && tw.idEqual(T_BASE, T_OURS))
                    add(T_THEIRS, DirCacheEntry.STAGE_0);
                else if (modeB == modeT && tw.idEqual(T_BASE, T_THEIRS))
                    add(T_OURS, DirCacheEntry.STAGE_0);
                else {
                    if (nonTree(modeB)) {
                        add(T_BASE, DirCacheEntry.STAGE_1);
                        hasConflict = true;
                    }
                    if (nonTree(modeO)) {
                        add(T_OURS, DirCacheEntry.STAGE_2);
                        hasConflict = true;
                    }
                    if (nonTree(modeT)) {
                        add(T_THEIRS, DirCacheEntry.STAGE_3);
                        hasConflict = true;
                    }
                    if (tw.isSubtree())
                        tw.enterSubtree();
                }
            }
            builder.finish();
            builder = null;

            if (hasConflict)
                return false;
            try {
                ObjectInserter odi = getObjectInserter();
                resultTree = cache.writeTree(odi);
                odi.flush();
                return true;
            } catch (UnmergedPathException upe) {
                resultTree = null;
                return false;
            }
        }

        private static boolean nonTree(int mode) {
            return mode != 0 && !FileMode.TREE.equals(mode);
        }

        private void add(int tree, int stage) throws IOException {
            final AbstractTreeIterator i = getTree(tree);
            if (i != null) {
                if (FileMode.TREE.equals(tw.getRawMode(tree))) {
                    builder.addTree(tw.getRawPath(), stage, reader, tw
                            .getObjectId(tree));
                } else {
                    final DirCacheEntry e;

                    e = new DirCacheEntry(tw.getRawPath(), stage);
                    e.setObjectIdFromRaw(i.idBuffer(), i.idOffset());
                    e.setFileMode(tw.getFileMode(tree));
                    builder.add(e);
                }
            }
        }

        private AbstractTreeIterator getTree(int tree) {
            return tw.getTree(tree, AbstractTreeIterator.class);
        }

        @Override
        public ObjectId getResultTreeId() {
            return resultTree;
        }
    }

}