LfsProtocolServlet: Add support for rate limit and bandwidth limit errors

The git-lfs specification [1] describes the following optional status codes
that may be returned:

429 - The user has hit a rate limit with the server. Though the API does
      not specify any rate limits, implementors are encouraged to set some
      for availability reasons.

509 - Returned if the bandwidth limit for the user or repository has been
      exceeded. The API does not specify any bandwidth limit, but implementors
      may track usage.

Add two new exception classes to represent these cases. Implementations may
throw these from #getLargeFileRepository(), causing the corresponding HTTP
status codes to be returned to the client.

[1] https://github.com/github/git-lfs/blob/master/docs/api/v1/http-v1-batch.md

Change-Id: I7b93f3cf90f7344c90b1587e07927fdeb167097e
Signed-off-by: David Pursehouse <david.pursehouse@gmail.com>

org.eclipse.jgit.lfs.server/src/org/eclipse/jgit/lfs/server/LfsProtocolServlet.java

@@ -63,7 +63,9 @@ import javax.servlet.http.HttpServlet;
 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;
 
+import org.eclipse.jgit.lfs.errors.LfsBandwidthLimitExceeded;
 import org.eclipse.jgit.lfs.errors.LfsException;
+import org.eclipse.jgit.lfs.errors.LfsRateLimitExceeded;
 import org.eclipse.jgit.lfs.errors.LfsRepositoryNotFound;
 import org.eclipse.jgit.lfs.errors.LfsRepositoryReadOnly;
 import org.eclipse.jgit.lfs.errors.LfsValidationError;
@@ -86,6 +88,10 @@ public abstract class LfsProtocolServlet extends HttpServlet {
 	private static final String CONTENTTYPE_VND_GIT_LFS_JSON =
 			"application/vnd.git-lfs+json; charset=utf-8"; //$NON-NLS-1$
 
+	private static final int SC_RATE_LIMIT_EXCEEDED = 429;
+
+	private static final int SC_BANDWIDTH_LIMIT_EXCEEDED = 509;
+
 	private Gson gson = createGson();
 
 	/**
@@ -163,6 +169,10 @@ public abstract class LfsProtocolServlet extends HttpServlet {
 			sendError(res, w, SC_NOT_FOUND, e.getMessage());
 		} catch (LfsRepositoryReadOnly e) {
 			sendError(res, w, SC_FORBIDDEN, e.getMessage());
+		} catch (LfsRateLimitExceeded e) {
+			sendError(res, w, SC_RATE_LIMIT_EXCEEDED, e.getMessage());
+		} catch (LfsBandwidthLimitExceeded e) {
+			sendError(res, w, SC_BANDWIDTH_LIMIT_EXCEEDED, e.getMessage());
 		} catch (LfsException e) {
 			sendError(res, w, SC_SERVICE_UNAVAILABLE, e.getMessage());
 		} finally {

org.eclipse.jgit.lfs/src/org/eclipse/jgit/lfs/errors/LfsBandwidthLimitExceeded.java

@@ -0,0 +1,61 @@
+/*
+ * Copyright (C) 2016, David Pursehouse <david.pursehouse@gmail.com>
+ * 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.lfs.errors;
+
+/**
+ * Thrown when the bandwidth limit for the user or repository has been exceeded.
+ *
+ * @since 4.5
+ *
+ */
+public class LfsBandwidthLimitExceeded extends LfsException {
+	private static final long serialVersionUID = 1L;
+
+	/**
+	 * @param message
+	 */
+	public LfsBandwidthLimitExceeded(String message) {
+		super(message);
+	}
+}

org.eclipse.jgit.lfs/src/org/eclipse/jgit/lfs/errors/LfsRateLimitExceeded.java

@@ -0,0 +1,61 @@
+/*
+ * Copyright (C) 2016, David Pursehouse <david.pursehouse@gmail.com>
+ * 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.lfs.errors;
+
+/**
+ * Thrown when the user has hit a rate limit with the server.
+ *
+ * @since 4.5
+ *
+ */
+public class LfsRateLimitExceeded extends LfsException {
+	private static final long serialVersionUID = 1L;
+
+	/**
+	 * @param message
+	 */
+	public LfsRateLimitExceeded(String message) {
+		super(message);
+	}
+}