DiffIndexChanges.java

package org.dstadler.jgit.porcelain;

/*
   Copyright 2013, 2014 Dominik Stadler

   Licensed under the Apache License, Version 2.0 (the "License");
   you may not use this file except in compliance with the License.
   You may obtain a copy of the License at

     http://www.apache.org/licenses/LICENSE-2.0

   Unless required by applicable law or agreed to in writing, software
   distributed under the License is distributed on an "AS IS" BASIS,
   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   See the License for the specific language governing permissions and
   limitations under the License.
 */

import java.io.IOException;
import java.util.List;

import org.dstadler.jgit.helper.CookbookHelper;
import org.eclipse.jgit.api.Git;
import org.eclipse.jgit.api.errors.GitAPIException;
import org.eclipse.jgit.diff.DiffEntry;
import org.eclipse.jgit.dircache.DirCacheIterator;
import org.eclipse.jgit.lib.ObjectReader;
import org.eclipse.jgit.lib.Repository;
import org.eclipse.jgit.revwalk.RevCommit;
import org.eclipse.jgit.revwalk.RevTree;
import org.eclipse.jgit.revwalk.RevWalk;
import org.eclipse.jgit.treewalk.AbstractTreeIterator;
import org.eclipse.jgit.treewalk.CanonicalTreeParser;

/**
 * Simple snippet which shows how to diff HEAD with the current
 * "index".
 *
 * You may need to perform some local changes and add them to the index
 * in order to make this snippet show some diffs
 */
public class DiffIndexChanges {

    public static void main(String[] args) throws IOException, GitAPIException {
        try (Repository repository = CookbookHelper.openJGitCookbookRepository()) {
            try (Git git = new Git(repository)) {

                // compare older commit with the newer one, showing an addition
                // and 2 changes
                listDiff(git,
						prepareTreeParser(repository),
						new DirCacheIterator(git.getRepository().readDirCache()));
            }
        }
    }

	private static AbstractTreeIterator prepareTreeParser(Repository repository) throws IOException {
		// from the commit we can build the tree which allows us to construct the TreeParser
		//noinspection Duplicates
		try (RevWalk walk = new RevWalk(repository)) {
			RevCommit commit = walk.parseCommit(repository.resolve("HEAD"));
			RevTree tree = walk.parseTree(commit.getTree().getId());

			CanonicalTreeParser treeParser = new CanonicalTreeParser();
			try (ObjectReader reader = repository.newObjectReader()) {
				treeParser.reset(reader, tree.getId());
			}

			walk.dispose();

			return treeParser;
		}
	}

    private static void listDiff(Git git, AbstractTreeIterator oldTree, AbstractTreeIterator newTree) throws GitAPIException {
        final List<DiffEntry> diffs = git.diff()
                .setOldTree(oldTree)
                .setNewTree(newTree)
                .call();

		System.out.println();
		System.out.println("Found: " + diffs.size() + " differences between " + oldTree + " and " + newTree);
        for (DiffEntry diff : diffs) {
			CookbookHelper.printDiff(diff);
        }
    }
}