Catch and report "ERR message" during remote advertisements

GitHub broke the native git protocol a while ago by interjecting an
"ERR message" line into the upload-pack or receive-pack advertisement
list.  This didn't match the expected pattern, so it caused existing
C Git clients to abort with a protocol exception.

These days, C Git clients actually look for this message and abort
with a more graceful notice to the end-user.  JGit should do the
same, including setting up a custom exception type that makes it
easier for higher-level UIs to identify a message from the remote
site and present it to the user.

Change-Id: I51ab62a382cfaf1082210e8bfaa69506fd0d9786
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>

org.eclipse.jgit/src/org/eclipse/jgit/errors/RemoteRepositoryException.java

@@ -0,0 +1,70 @@
+/*
+ * Copyright (C) 2010, Google Inc.
+ * and other copyright owners as documented in the project's IP log.
+ *
+ * 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
+ *
+ * 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.
+ */
+
+package org.eclipse.jgit.errors;
+
+import org.eclipse.jgit.transport.URIish;
+
+/**
+ * Contains a message from the remote repository indicating a problem.
+ * <p>
+ * Some remote repositories may send customized error messages describing why
+ * they cannot be accessed. These messages are wrapped up in this exception and
+ * thrown to the caller of the transport operation.
+ */
+public class RemoteRepositoryException extends TransportException {
+	private static final long serialVersionUID = 1L;
+
+	/**
+	 * Constructs a RemoteRepositoryException for a message.
+	 *
+	 * @param uri
+	 *            URI used for transport
+	 * @param message
+	 *            message, exactly as supplied by the remote repository. May
+	 *            contain LFs (newlines) if the remote formatted it that way.
+	 */
+	public RemoteRepositoryException(URIish uri, String message) {
+		super(uri, message);
+	}
+}

org.eclipse.jgit/src/org/eclipse/jgit/transport/BasePackConnection.java

@@ -59,6 +59,7 @@ import java.util.Set;
 
 import org.eclipse.jgit.errors.NoRemoteRepositoryException;
 import org.eclipse.jgit.errors.PackProtocolException;
+import org.eclipse.jgit.errors.RemoteRepositoryException;
 import org.eclipse.jgit.errors.TransportException;
 import org.eclipse.jgit.lib.ObjectId;
 import org.eclipse.jgit.lib.ObjectIdRef;
@@ -149,6 +150,19 @@ abstract class BasePackConnection extends BaseConnection {
 		outNeedsEnd = true;
 	}
 
+	/**
+	 * Reads the advertised references through the initialized stream.
+	 * <p>
+	 * Subclass implementations may call this method only after setting up the
+	 * input and output streams with {@link #init(InputStream, OutputStream)}.
+	 * <p>
+	 * If any errors occur, this connection is automatically closed by invoking
+	 * {@link #close()} and the exception is wrapped (if necessary) and thrown
+	 * as a {@link TransportException}.
+	 *
+	 * @throws TransportException
+	 *             the reference list could not be scanned.
+	 */
 	protected void readAdvertisedRefs() throws TransportException {
 		try {
 			readAdvertisedRefsImpl();
@@ -179,6 +193,12 @@ abstract class BasePackConnection extends BaseConnection {
 			if (line == PacketLineIn.END)
 				break;
 
+			if (line.startsWith("ERR ")) {
+				// This is a customized remote service error.
+				// Users should be informed about it.
+				throw new RemoteRepositoryException(uri, line.substring(4));
+			}
+
 			if (avail.isEmpty()) {
 				final int nul = line.indexOf('\0');
 				if (nul >= 0) {