Support LFS protocol and a file system based LFS storage

Implement LfsProtocolServlet handling the "Git LFS v1 Batch API"
protocol [1]. Add a simple file system based LFS content store and the
debug-lfs-store command to simplify testing.

Introduce a LargeFileRepository interface to enable additional storage
implementation while reusing the same protocol implementation.

At the client side we have to configure the lfs.url, specify that
we use the batch API and we don't use authentication:

  [lfs]
	  url = http://host:port/lfs
	  batch = true
  [lfs "http://host:port/lfs"]
	  access = none

the git-lfs client appends the "objects/batch" to the lfs.url.

Hard code an Authorization header in the FileLfsRepository.getAction
because then git-lfs client will skip asking for credentials. It will
just forward the Authorization header from the response to the
download/upload request.

The FileLfsServlet supports file content storage for "Large File
Storage" (LFS) server as defined by the Github LFS API [2].

- upload and download of large files is probably network bound hence use
  an asynchronous servlet for good scalability
- simple object storage in file system with 2 level fan-out
- use LockFile to protect writing large objects against multiple
  concurrent uploads of the same object
- to prevent corrupt uploads the uploaded file is rejected if its hash
  doesn't match id given in URL

The debug-lfs-store command is used to run the LfsProtocolServlet and,
optionally, the FileLfsServlet which makes it easier to setup a
local test server.

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

Bug: 472961
Change-Id: I7378da5575159d2195138d799704880c5c82d5f3
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>
Signed-off-by: Sasa Zivkov <sasa.zivkov@sap.com>

2 files changed, 109 insertions, 1 deletions

diff --git a/org.eclipse.jgit.lfs/src/org/eclipse/jgit/lfs/errors/CorruptLongObjectException.java b/org.eclipse.jgit.lfs/src/org/eclipse/jgit/lfs/errors/CorruptLongObjectException.java
new file mode 100644
index 0000000000..fea148b884
--- /dev/null
+++ b/org.eclipse.jgit.lfs/src/org/eclipse/jgit/lfs/errors/CorruptLongObjectException.java
@@ -0,0 +1,96 @@
+/*
+ * Copyright (C) 2015, Matthias Sohn <matthias.sohn@sap.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;
+
+import org.eclipse.jgit.lfs.lib.AnyLongObjectId;
+
+/**
+ * Thrown when an object id is given that doesn't match the hash of the object's
+ * content
+ *
+ * @since 4.3
+ */
+public class CorruptLongObjectException extends IllegalArgumentException {
+
+	private static final long serialVersionUID = 1L;
+
+	private final AnyLongObjectId id;
+
+	private final AnyLongObjectId contentHash;
+
+	/**
+	 * Corrupt long object detected.
+	 *
+	 * @param id
+	 *            id of the long object
+	 * @param contentHash
+	 *            hash of the long object's content
+	 *
+	 * @param message
+	 */
+	public CorruptLongObjectException(AnyLongObjectId id,
+			AnyLongObjectId contentHash,
+			String message) {
+		super(message);
+		this.id = id;
+		this.contentHash = contentHash;
+	}
+
+	/**
+	 * @return the id of the object, i.e. the expected hash of the object's
+	 *         content
+	 */
+	public AnyLongObjectId getId() {
+		return id;
+	}
+
+	/**
+	 * @return the actual hash of the object's content which doesn't match the
+	 *         object's id when this exception is thrown which signals that the
+	 *         object has been corrupted
+	 */
+	public AnyLongObjectId getContentHash() {
+		return contentHash;
+	}
+}
diff --git a/org.eclipse.jgit.lfs/src/org/eclipse/jgit/lfs/lib/Constants.java b/org.eclipse.jgit.lfs/src/org/eclipse/jgit/lfs/lib/Constants.java
index 92a5c4250f..3cadbf73a1 100644
--- a/org.eclipse.jgit.lfs/src/org/eclipse/jgit/lfs/lib/Constants.java
+++ b/org.eclipse.jgit.lfs/src/org/eclipse/jgit/lfs/lib/Constants.java
@@ -99,4 +99,16 @@ public final class Constants {
 			throw new LinkageError(
 					LfsText.get().incorrectLONG_OBJECT_ID_LENGTH);
 	}
-}
+
+	/**
+	 * Content type used by LFS REST API as defined in
+	 * {@link "https://github.com/github/git-lfs/blob/master/docs/api/http-v1-batch.md"}
+	 */
+	public static String CONTENT_TYPE_GIT_LFS_JSON = "application/vnd.git-lfs+json";
+
+	/**
+	 * "arbitrary binary data" as defined in RFC 2046
+	 * {@link "https://www.ietf.org/rfc/rfc2046.txt"}
+	 */
+	public static String HDR_APPLICATION_OCTET_STREAM = "application/octet-stream";
+}
\ No newline at end of file