TagCommand: propagate NO_CHANGE information

Some clients may wish to allow NO_CHANGE lightweight tag updates
without setting the force flag. (For instance EGit does so.)
Command-line git does not allow this.

Propagate the RefUpdate result via the RefAlreadyExistsException.
That way a client has the possibility to catch it and check the
failure reason without having to parse the exception message, and
take appropriate action, like ignoring the exception on NO_CHANGE.

Change-Id: I60e7a15a3c309db4106cab87847a19b6d24866f6
Signed-off-by: Thomas Wolf <thomas.wolf@paranor.ch>

org.eclipse.jgit.test/tst/org/eclipse/jgit/api/TagCommandTest.java

 import org.eclipse.jgit.api.errors.RefAlreadyExistsException;
 import org.eclipse.jgit.junit.RepositoryTestCase;
 import org.eclipse.jgit.lib.Ref;
+import org.eclipse.jgit.lib.RefUpdate;
 import org.eclipse.jgit.lib.Repository;
 import org.eclipse.jgit.revwalk.RevCommit;
 import org.eclipse.jgit.revwalk.RevWalk;
 					.setAnnotated(false).call();
 			assertEquals(commit.getId(), tagRef.getObjectId());
 			// Without force, we want to get a RefAlreadyExistsException
-			assertThrows(RefAlreadyExistsException.class,
+			RefAlreadyExistsException e = assertThrows(
+					RefAlreadyExistsException.class,
 					() -> git.tag().setObjectId(commit).setName("tag")
 							.setAnnotated(false).call());
+			assertEquals(RefUpdate.Result.NO_CHANGE, e.getUpdateResult());
 			// With force the call should work
 			assertEquals(commit.getId(),
 					git.tag().setObjectId(commit).setName("tag")

org.eclipse.jgit/src/org/eclipse/jgit/api/TagCommand.java

 				return repo.exactRef(refName);
 			}
 			throw new RefAlreadyExistsException(MessageFormat
-					.format(JGitText.get().tagAlreadyExists, newTagToString));
+					.format(JGitText.get().tagAlreadyExists, newTagToString),
+					updateResult);
 		case REJECTED:
 			throw new RefAlreadyExistsException(MessageFormat.format(
-					JGitText.get().tagAlreadyExists, newTagToString));
+					JGitText.get().tagAlreadyExists, newTagToString),
+					updateResult);
 		default:
 			throw new JGitInternalException(MessageFormat.format(
 					JGitText.get().updatingRefFailed, refName, newTagToString,

org.eclipse.jgit/src/org/eclipse/jgit/api/errors/RefAlreadyExistsException.java

 /*
- * Copyright (C) 2010,Mathias Kinzler <mathias.kinzler@sap.com> and
- * other copyright owners as documented in the project's IP log.
+ * Copyright (C) 2010, 2020 Mathias Kinzler <mathias.kinzler@sap.com> and others
  *
  * This program and the accompanying materials are made available under the
- * terms of the Eclipse Distribution License v1.0 which accompanies this
- * distribution, is reproduced below, and is available at
- * http://www.eclipse.org/org/documents/edl-v10.php
+ * terms of the Eclipse Distribution License v. 1.0 which is available at
+ * https://www.eclipse.org/org/documents/edl-v10.php.
  *
- * All rights reserved.
- *
- * Redistribution and use in source and binary forms, with or without
- * modification, are permitted provided that the following conditions are met:
- *
- * - Redistributions of source code must retain the above copyright notice, this
- * list of conditions and the following disclaimer.
- *
- * - Redistributions in binary form must reproduce the above copyright notice,
- * this list of conditions and the following disclaimer in the documentation
- * and/or other materials provided with the distribution.
- *
- * - Neither the name of the Eclipse Foundation, Inc. nor the names of its
- * contributors may be used to endorse or promote products derived from this
- * software without specific prior written permission.
- *
- * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
- * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
- * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
- * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
- * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
- * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
- * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
- * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
- * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
- * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
- * POSSIBILITY OF SUCH DAMAGE.
+ * SPDX-License-Identifier: BSD-3-Clause
  */
 package org.eclipse.jgit.api.errors;
 
+import org.eclipse.jgit.annotations.Nullable;
+import org.eclipse.jgit.lib.RefUpdate;
+
 /**
  * Thrown when trying to create a {@link org.eclipse.jgit.lib.Ref} with the same
  * name as an existing one
 public class RefAlreadyExistsException extends GitAPIException {
 	private static final long serialVersionUID = 1L;
 
+	private final RefUpdate.Result updateResult;
+
 	/**
-	 * Constructor for RefAlreadyExistsException
+	 * Creates a new instance with the given message.
 	 *
 	 * @param message
 	 *            error message
 	 */
 	public RefAlreadyExistsException(String message) {
+		this(message, null);
+	}
+
+	/**
+	 * Constructor for RefAlreadyExistsException
+	 *
+	 * @param message
+	 *            error message
+	 * @param updateResult
+	 *            that caused the exception; may be {@code null}
+	 * @since 5.11
+	 */
+	public RefAlreadyExistsException(String message,
+			@Nullable RefUpdate.Result updateResult) {
 		super(message);
+		this.updateResult = updateResult;
+	}
+
+	/**
+	 * Retrieves the {@link org.eclipse.jgit.lib.RefUpdate.Result
+	 * RefUpdate.Result} that caused the exception.
+	 *
+	 * @return the {@link org.eclipse.jgit.lib.RefUpdate.Result
+	 *         RefUpdate.Result} or {@code null} if unknown
+	 * @since 5.11
+	 */
+	@Nullable
+	public RefUpdate.Result getUpdateResult() {
+		return updateResult;
 	}
 }