Enhance ResetCommand to allow disabling reflog update

This will be used by EGit for implementing commit amend in the staging
view (see Idcd1efeeee8b3065bae36e285bfc0af24ab1e88f).

Change-Id: Ice9ebbb1c0c3314c679f4db40cdd3664f61c27c3
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

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

 		assertEquals(prevHead, db.readOrigHead());
 	}
 
+	@Test
+	public void testHardResetReflogDisabled() throws Exception {
+		setupRepository();
+		ObjectId prevHead = db.resolve(Constants.HEAD);
+		ResetCommand reset = git.reset();
+		assertSameAsHead(reset.setMode(ResetType.HARD)
+				.setRef(initialCommit.getName()).disableRefLog(true).call());
+		assertTrue("reflog should be disabled", reset.isReflogDisabled());
+		// check if HEAD points to initial commit now
+		ObjectId head = db.resolve(Constants.HEAD);
+		assertEquals(initialCommit, head);
+		// check if files were removed
+		assertFalse(indexFile.exists());
+		assertTrue(untrackedFile.exists());
+		// fileInIndex must no longer be in HEAD and in the index
+		String fileInIndexPath = indexFile.getAbsolutePath();
+		assertFalse(inHead(fileInIndexPath));
+		assertFalse(inIndex(indexFile.getName()));
+		assertReflogDisabled(head);
+		assertEquals(prevHead, db.readOrigHead());
+	}
+
 	@Test
 	public void testHardResetWithConflicts_DoOverWriteUntrackedFile()
 			throws JGitInternalException,
 				.getName());
 	}
 
+	private void assertReflogDisabled(ObjectId head)
+			throws IOException {
+		// Check the reflog for HEAD
+		String actualHeadMessage = db.getReflogReader(Constants.HEAD)
+				.getLastEntry().getComment();
+		String expectedHeadMessage = "commit: adding a.txt and dir/b.txt";
+		assertEquals(expectedHeadMessage, actualHeadMessage);
+		assertEquals(head.getName(), db.getReflogReader(Constants.HEAD)
+				.getLastEntry().getOldId().getName());
+
+		// The reflog for master contains the same as the one for HEAD
+		String actualMasterMessage = db.getReflogReader("refs/heads/master")
+				.getLastEntry().getComment();
+		String expectedMasterMessage = "commit: adding a.txt and dir/b.txt";
+		assertEquals(expectedMasterMessage, actualMasterMessage);
+		assertEquals(head.getName(), db.getReflogReader(Constants.HEAD)
+				.getLastEntry().getOldId().getName());
+	}
 	/**
 	 * Checks if a file with the given path exists in the HEAD tree
 	 *

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

 
 	private Collection<String> filepaths = new LinkedList<String>();
 
+	private boolean isReflogDisabled;
+
 	/**
 	 *
 	 * @param repo
 				ru.setNewObjectId(commitId);
 
 				String refName = Repository.shortenRefName(getRefOrHEAD());
-				String message = refName + ": updating " + Constants.HEAD; //$NON-NLS-1$
-				ru.setRefLogMessage(message, false);
+				if (isReflogDisabled) {
+					ru.disableRefLog();
+				} else {
+					String message = refName + ": updating " + Constants.HEAD; //$NON-NLS-1$
+					ru.setRefLogMessage(message, false);
+				}
 				if (ru.forceUpdate() == RefUpdate.Result.LOCK_FAILURE)
 					throw new JGitInternalException(MessageFormat.format(
 							JGitText.get().cannotLock, ru.getName()));
 		return this;
 	}
 
+	/**
+	 * @param disable
+	 *            if {@code true} disables writing a reflog entry for this reset
+	 *            command
+	 * @return this instance
+	 * @since 4.5
+	 */
+	public ResetCommand disableRefLog(boolean disable) {
+		this.isReflogDisabled = disable;
+		return this;
+	}
+
+	/**
+	 * @return {@code true} if writing reflog is disabled for this reset command
+	 * @since 4.5
+	 */
+	public boolean isReflogDisabled() {
+		return this.isReflogDisabled;
+	}
+
 	private String getRefOrHEAD() {
 		if (ref != null)
 			return ref;