<summary>New method for updating a reference (branch) to a new commit id.</summary>

            <version major="1" minor="24"/>

            <date day="19" month="6" year="2014"/>

            <author login="ovrabec"/>

            <compatibility addition="yes"/>

            <description>

                <p>In order to simplify a trivial use-case of merging a remote branch into a local branch

                    not currently checked-out we're adding a new method able to update the local branch to

                    the new id. It is possible only if the branch requires a fast-forward merge (does not

                    contain any unpushed commits).

                </p>

            </description>

            <class package="org.netbeans.libs.git" name="GitClient"/>

            <issue number="245078"/>

        </change>

        <change>

            <api name="gitlibrary_api"/>

import org.netbeans.libs.git.jgit.commands.UpdateRefCommand;

    /**

     * Updates a given reference to a new id. If the new id is also a ref then

     * the ref will be updated to the same commit id referenced by the new id.

     * The update will not be permitted if the reference is not merged into the

     * new commit (i.e. contains its private commits).

     *

     * @param referenceName name of the ref to update

     * @param newId the new reference id

     * @param monitor progress monitor

     * @return result result of the update

     * @throws GitException an unexpected error happens

     */

    public GitRefUpdateResult updateReference (String referenceName, String newId, ProgressMonitor monitor) throws GitException {

        Repository repository = gitRepository.getRepository();

        UpdateRefCommand cmd = new UpdateRefCommand(repository, getClassFactory(), referenceName, newId, monitor);

        cmd.execute();

        return cmd.getResult();

    }

/*

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.

 *

 * Copyright 2010 Oracle and/or its affiliates. All rights reserved.

 *

 * Oracle and Java are registered trademarks of Oracle and/or its affiliates.

 * Other names may be trademarks of their respective owners.

 *

 * The contents of this file are subject to the terms of either the GNU

 * General Public License Version 2 only ("GPL") or the Common

 * Development and Distribution License("CDDL") (collectively, the

 * "License"). You may not use this file except in compliance with the

 * License. You can obtain a copy of the License at

 * http://www.netbeans.org/cddl-gplv2.html

 * or nbbuild/licenses/CDDL-GPL-2-CP. See the License for the

 * specific language governing permissions and limitations under the

 * License.  When distributing the software, include this License Header

 * Notice in each file and include the License file at

 * nbbuild/licenses/CDDL-GPL-2-CP.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the GPL Version 2 section of the License file that

 * accompanied this code. If applicable, add the following below the

 * License Header, with the fields enclosed by brackets [] replaced by

 * your own identifying information:

 * "Portions Copyrighted [year] [name of copyright owner]"

 *

 * If you wish your version of this file to be governed by only the CDDL

 * or only the GPL Version 2, indicate your decision by adding

 * "[Contributor] elects to include this software in this distribution

 * under the [CDDL or GPL Version 2] license." If you do not indicate a

 * single choice of license, a recipient has the option to distribute

 * your version of this file under either the CDDL, the GPL Version 2 or

 * to extend the choice of license to its licensees as provided above.

 * However, if you add GPL Version 2 code and therefore, elected the GPL

 * Version 2 license, then the option applies only if the new code is

 * made subject to such option by the copyright holder.

 *

 * Contributor(s):

 *

 * Portions Copyrighted 2010 Sun Microsystems, Inc.

 */

package org.netbeans.libs.git.jgit.commands;

import java.io.IOException;

import org.eclipse.jgit.lib.ObjectId;

import org.eclipse.jgit.lib.ObjectIdRef;

import org.eclipse.jgit.lib.Ref;

import org.eclipse.jgit.lib.RefUpdate;

import org.eclipse.jgit.lib.Repository;

import org.netbeans.libs.git.GitException;

import org.netbeans.libs.git.GitRefUpdateResult;

import org.netbeans.libs.git.jgit.GitClassFactory;

import org.netbeans.libs.git.progress.ProgressMonitor;

/**

 *

 * @author ondra

 */

public class UpdateRefCommand extends GitCommand {

    private final String revision;

    private final String refName;

    private GitRefUpdateResult result;

    public UpdateRefCommand (Repository repository, GitClassFactory gitFactory, String refName, String revision, ProgressMonitor monitor) {

        super(repository, gitFactory, monitor);

        this.refName = refName;

        this.revision = revision;

    }

    @Override

    protected void run () throws GitException {

        Repository repository = getRepository();

        try {

            Ref ref = repository.getRef(refName);

            if (ref == null || ref.isSymbolic()) {

                // currently unable to update symbolic references

                result = GitRefUpdateResult.valueOf(RefUpdate.Result.NOT_ATTEMPTED.name());

                return;

            }

            Ref newRef = repository.getRef(revision);

            String name;

            if (newRef == null) {

                ObjectId id = repository.resolve(revision);

                newRef = new ObjectIdRef.Unpeeled(Ref.Storage.LOOSE, id.name(),id.copy());

                name = newRef.getName();

            } else {

                name = revision;

            }

            RefUpdate u = repository.updateRef(ref.getName());

            u.setNewObjectId(newRef.isPeeled() ? newRef.getPeeledObjectId() : newRef.getObjectId());

            u.setRefLogMessage("merge " + name + ": Fast-forward", false); //NOI18N

            u.update();

            result = GitRefUpdateResult.valueOf((u.getResult() == null 

                ? RefUpdate.Result.NOT_ATTEMPTED

                : u.getResult()).name());

        } catch (IOException ex) {

            throw new GitException(ex);

        }

    }

    @Override

    protected String getCommandDescription () {

        return new StringBuilder("git update-ref ").append(refName).append(revision).toString(); //NOI18N

    }

    public GitRefUpdateResult getResult () {

        return result;

    }

}

import org.netbeans.libs.git.jgit.commands.UpdateRefTest;

        suite.addTestSuite(UpdateRefTest.class);

/*

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.

 *

 * Copyright 2010 Oracle and/or its affiliates. All rights reserved.

 *

 * Oracle and Java are registered trademarks of Oracle and/or its affiliates.

 * Other names may be trademarks of their respective owners.

 *

 * The contents of this file are subject to the terms of either the GNU

 * General Public License Version 2 only ("GPL") or the Common

 * Development and Distribution License("CDDL") (collectively, the

 * "License"). You may not use this file except in compliance with the

 * License. You can obtain a copy of the License at

 * http://www.netbeans.org/cddl-gplv2.html

 * or nbbuild/licenses/CDDL-GPL-2-CP. See the License for the

 * specific language governing permissions and limitations under the

 * License.  When distributing the software, include this License Header

 * Notice in each file and include the License file at

 * nbbuild/licenses/CDDL-GPL-2-CP.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the GPL Version 2 section of the License file that

 * accompanied this code. If applicable, add the following below the

 * License Header, with the fields enclosed by brackets [] replaced by

 * your own identifying information:

 * "Portions Copyrighted [year] [name of copyright owner]"

 *

 * If you wish your version of this file to be governed by only the CDDL

 * or only the GPL Version 2, indicate your decision by adding

 * "[Contributor] elects to include this software in this distribution

 * under the [CDDL or GPL Version 2] license." If you do not indicate a

 * single choice of license, a recipient has the option to distribute

 * your version of this file under either the CDDL, the GPL Version 2 or

 * to extend the choice of license to its licensees as provided above.

 * However, if you add GPL Version 2 code and therefore, elected the GPL

 * Version 2 license, then the option applies only if the new code is

 * made subject to such option by the copyright holder.

 *

 * Contributor(s):

 *

 * Portions Copyrighted 2010 Sun Microsystems, Inc.

 */

package org.netbeans.libs.git.jgit.commands;

import java.io.File;

import java.io.IOException;

import org.eclipse.jgit.lib.ReflogReader;

import org.eclipse.jgit.lib.Repository;

import org.netbeans.libs.git.GitClient;

import org.netbeans.libs.git.GitRefUpdateResult;

import org.netbeans.libs.git.GitRevisionInfo;

import org.netbeans.libs.git.jgit.AbstractGitTestCase;

/**

 *

 * @author ondra

 */

public class UpdateRefTest extends AbstractGitTestCase {

    private Repository repository;

    private File workDir;

    public UpdateRefTest (String testName) throws IOException {

        super(testName);

    }

    @Override

    protected void setUp() throws Exception {

        super.setUp();

        workDir = getWorkingDirectory();

        repository = getRepository(getLocalGitRepository());

    }

    public void testNotAttempted () throws Exception {

        File f = new File(workDir, "f");

        write(f, "init");

        add(f);

        commit(f);

        write(f, "modi");

        add(f);

        commit(f);

        GitClient client = getClient(workDir);

        GitRevisionInfo info = client.log("HEAD", NULL_PROGRESS_MONITOR);

        client.reset("HEAD~1", GitClient.ResetType.HARD, NULL_PROGRESS_MONITOR);

        GitRefUpdateResult res = client.updateReference("HEAD", info.getRevision(), NULL_PROGRESS_MONITOR);

        assertEquals(GitRefUpdateResult.NOT_ATTEMPTED, res);

    }

    public void testMoveMergeCommit () throws Exception {

        File f = new File(workDir, "f");

        write(f, "init");

        add(f);

        commit(f);

        write(f, "modif");

        add(f);

        commit(f);

        GitClient client = getClient(workDir);

        GitRevisionInfo info = client.log("HEAD", NULL_PROGRESS_MONITOR);

        client.reset("HEAD~1", GitClient.ResetType.HARD, NULL_PROGRESS_MONITOR);

        GitRefUpdateResult res = client.updateReference("master", info.getRevision(), NULL_PROGRESS_MONITOR);

        assertEquals(GitRefUpdateResult.FAST_FORWARD, res);

        ReflogReader reflogReader = repository.getReflogReader("master");

        assertEquals("merge " + info.getRevision() + ": Fast-forward", reflogReader.getLastEntry().getComment());

    }

    public void testMoveMergeRef () throws Exception {

        File f = new File(workDir, "f");

        write(f, "init");

        add(f);

        commit(f);

        write(f, "modif");

        add(f);

        commit(f);

        GitClient client = getClient(workDir);

        client.createBranch("BRANCH", "HEAD", NULL_PROGRESS_MONITOR);

        client.reset("HEAD~1", GitClient.ResetType.HARD, NULL_PROGRESS_MONITOR);

        GitRefUpdateResult res = client.updateReference("master", "BRANCH", NULL_PROGRESS_MONITOR);

        assertEquals(GitRefUpdateResult.FAST_FORWARD, res);

        ReflogReader reflogReader = repository.getReflogReader("master");

        assertEquals("merge BRANCH: Fast-forward", reflogReader.getLastEntry().getComment());

    }

    // must fail if would end in a non FF update

    public void testMoveMergeRejected () throws Exception {

        File f = new File(workDir, "f");

        write(f, "init");

        add(f);

        commit(f);

        write(f, "modif");

        add(f);

        commit(f);

        GitClient client = getClient(workDir);

        client.createBranch("BRANCH", "HEAD", NULL_PROGRESS_MONITOR);

        client.reset("HEAD~1", GitClient.ResetType.HARD, NULL_PROGRESS_MONITOR);

        write(f, "modif2");

        add(f);

        commit(f);

        GitRefUpdateResult res = client.updateReference("master", "BRANCH", NULL_PROGRESS_MONITOR);

        assertEquals(GitRefUpdateResult.REJECTED, res);

    }

}