LFS: pre-push upload support

If JGit built in LFS support is enabled for the current repository (or
user/system), any existing pre-push hook will cause an exception for the
time beeing, as only a single pre-push hook is supported.

Thus either native pre-push hooks OR JGit built-in LFS support may be
enabled currently, but not both.

Change-Id: Ie7d2b90e26e948d9cca3d05a7a19489488c75895
Signed-off-by: Markus Duft <markus.duft@ssi-schaefer.com>
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

8 files changed, 616 insertions, 183 deletions

diff --git a/org.eclipse.jgit.lfs/.settings/.api_filters b/org.eclipse.jgit.lfs/.settings/.api_filters
new file mode 100644
index 0000000000..097fd20658
--- /dev/null
+++ b/org.eclipse.jgit.lfs/.settings/.api_filters
@@ -0,0 +1,11 @@
+<?xml version="1.0" encoding="UTF-8" standalone="no"?>
+<component id="org.eclipse.jgit.lfs" version="2">
+    <resource path="src/org/eclipse/jgit/lfs/LfsPointer.java" type="org.eclipse.jgit.lfs.LfsPointer">
+        <filter id="336658481">
+            <message_arguments>
+                <message_argument value="org.eclipse.jgit.lfs.LfsPointer"/>
+                <message_argument value="SIZE_THRESHOLD"/>
+            </message_arguments>
+        </filter>
+    </resource>
+</component>
diff --git a/org.eclipse.jgit.lfs/META-INF/MANIFEST.MF b/org.eclipse.jgit.lfs/META-INF/MANIFEST.MF
index 740d7bbb12..798fccdfc4 100644
--- a/org.eclipse.jgit.lfs/META-INF/MANIFEST.MF
+++ b/org.eclipse.jgit.lfs/META-INF/MANIFEST.MF
@@ -16,11 +16,14 @@ Import-Package: com.google.gson;version="[2.8.2,3.0.0)",
  org.apache.http.impl.client;version="[4.2.6,5.0.0)",
  org.apache.http.impl.conn;version="[4.2.6,5.0.0)",
  org.eclipse.jgit.annotations;version="[4.11.0,4.12.0)";resolution:=optional,
+ org.eclipse.jgit.api.errors;version="[4.11.0,4.12.0)",
  org.eclipse.jgit.attributes;version="[4.11.0,4.12.0)",
  org.eclipse.jgit.errors;version="[4.11.0,4.12.0)",
+ org.eclipse.jgit.hooks;version="[4.11.0,4.12.0)",
  org.eclipse.jgit.internal.storage.file;version="[4.11.0,4.12.0)",
  org.eclipse.jgit.lib;version="[4.11.0,4.12.0)",
  org.eclipse.jgit.nls;version="[4.11.0,4.12.0)",
+ org.eclipse.jgit.revwalk;version="[4.11.0,4.12.0)",
  org.eclipse.jgit.storage.file;version="[4.11.0,4.12.0)",
  org.eclipse.jgit.transport;version="[4.11.0,4.12.0)",
  org.eclipse.jgit.transport.http;version="[4.11.0,4.12.0)",
diff --git a/org.eclipse.jgit.lfs/resources/org/eclipse/jgit/lfs/internal/LfsText.properties b/org.eclipse.jgit.lfs/resources/org/eclipse/jgit/lfs/internal/LfsText.properties
index 19d5ec587f..29cee3a8e0 100644
--- a/org.eclipse.jgit.lfs/resources/org/eclipse/jgit/lfs/internal/LfsText.properties
+++ b/org.eclipse.jgit.lfs/resources/org/eclipse/jgit/lfs/internal/LfsText.properties
@@ -14,4 +14,5 @@ lfsFailedToGetRepository=failed to get repository {0}
 lfsNoDownloadUrl="Need to download object from LFS server but couldn't determine LFS server URL"
 serverFailure=When trying to open a connection to {0} the server responded with an error code. rc={1}
 wrongAmoutOfDataReceived=While downloading data from the content server {0} {1} bytes have been received while {2} have been expected
-userConfigInvalid="User config file {0} invalid {1}"
\ No newline at end of file
+userConfigInvalid="User config file {0} invalid {1}"
+missingLocalObject="Local Object {0} is missing"
\ No newline at end of file
diff --git a/org.eclipse.jgit.lfs/src/org/eclipse/jgit/lfs/LfsPointer.java b/org.eclipse.jgit.lfs/src/org/eclipse/jgit/lfs/LfsPointer.java
index 360453116f..0e3830c098 100644
--- a/org.eclipse.jgit.lfs/src/org/eclipse/jgit/lfs/LfsPointer.java
+++ b/org.eclipse.jgit.lfs/src/org/eclipse/jgit/lfs/LfsPointer.java
@@ -64,7 +64,7 @@ import org.eclipse.jgit.lfs.lib.LongObjectId;
  *
  * @since 4.6
  */
-public class LfsPointer {
+public class LfsPointer implements Comparable<LfsPointer> {
 	/**
 	 * The version of the LfsPointer file format
 	 */
@@ -77,6 +77,13 @@ public class LfsPointer {
 	public static final String VERSION_LEGACY = "https://hawser.github.com/spec/v1"; //$NON-NLS-1$
 
 	/**
+	 * Don't inspect files that are larger than this threshold to avoid
+	 * excessive reading. No pointer file should be larger than this.
+	 * @since 4.11
+	 */
+	public static final int SIZE_THRESHOLD = 200;
+
+	/**
 	 * The name of the hash function as used in the pointer files. This will
 	 * evaluate to "sha256"
 	 */
@@ -185,5 +192,18 @@ public class LfsPointer {
 		return "LfsPointer: oid=" + oid.name() + ", size=" //$NON-NLS-1$ //$NON-NLS-2$
 				+ size;
 	}
+
+	/**
+	 * @since 4.11
+	 */
+	@Override
+	public int compareTo(LfsPointer o) {
+		int x = getOid().compareTo(o.getOid());
+		if (x != 0) {
+			return x;
+		}
+
+		return (int) (getSize() - o.getSize());
+	}
 }
 
diff --git a/org.eclipse.jgit.lfs/src/org/eclipse/jgit/lfs/LfsPrePushHook.java b/org.eclipse.jgit.lfs/src/org/eclipse/jgit/lfs/LfsPrePushHook.java
new file mode 100644
index 0000000000..ffc1ee39a7
--- /dev/null
+++ b/org.eclipse.jgit.lfs/src/org/eclipse/jgit/lfs/LfsPrePushHook.java
@@ -0,0 +1,272 @@
+/*
+ * Copyright (C) 2017, Markus Duft <markus.duft@ssi-schaefer.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;
+
+import static java.nio.charset.StandardCharsets.UTF_8;
+import static org.eclipse.jgit.lfs.internal.LfsConnectionFactory.toRequest;
+import static org.eclipse.jgit.lfs.Protocol.OPERATION_UPLOAD;
+import static org.eclipse.jgit.transport.http.HttpConnection.HTTP_OK;
+import static org.eclipse.jgit.util.HttpSupport.METHOD_POST;
+import static org.eclipse.jgit.util.HttpSupport.METHOD_PUT;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.InputStreamReader;
+import java.io.OutputStream;
+import java.io.PrintStream;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.text.MessageFormat;
+import java.util.Collection;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+import java.util.TreeSet;
+
+import org.eclipse.jgit.api.errors.AbortedByHookException;
+import org.eclipse.jgit.errors.IncorrectObjectTypeException;
+import org.eclipse.jgit.errors.MissingObjectException;
+import org.eclipse.jgit.hooks.PrePushHook;
+import org.eclipse.jgit.lfs.Protocol.ObjectInfo;
+import org.eclipse.jgit.lfs.errors.CorruptMediaFile;
+import org.eclipse.jgit.lfs.internal.LfsConnectionFactory;
+import org.eclipse.jgit.lfs.internal.LfsText;
+import org.eclipse.jgit.lib.AnyObjectId;
+import org.eclipse.jgit.lib.Constants;
+import org.eclipse.jgit.lib.ObjectId;
+import org.eclipse.jgit.lib.ObjectReader;
+import org.eclipse.jgit.lib.Ref;
+import org.eclipse.jgit.lib.RefDatabase;
+import org.eclipse.jgit.lib.Repository;
+import org.eclipse.jgit.revwalk.ObjectWalk;
+import org.eclipse.jgit.revwalk.RevObject;
+import org.eclipse.jgit.transport.RemoteRefUpdate;
+import org.eclipse.jgit.transport.http.HttpConnection;
+
+import com.google.gson.Gson;
+import com.google.gson.stream.JsonReader;
+
+/**
+ * Pre-push hook that handles uploading LFS artefacts.
+ *
+ * @since 4.11
+ */
+public class LfsPrePushHook extends PrePushHook {
+
+	private static final String EMPTY = ""; //$NON-NLS-1$
+	private Collection<RemoteRefUpdate> refs;
+
+	/**
+	 * @param repo
+	 *            the repository
+	 * @param outputStream
+	 *            not used by this implementation
+	 */
+	public LfsPrePushHook(Repository repo, PrintStream outputStream) {
+		super(repo, outputStream);
+	}
+
+	@Override
+	public void setRefs(Collection<RemoteRefUpdate> toRefs) {
+		this.refs = toRefs;
+	}
+
+	@Override
+	public String call() throws IOException, AbortedByHookException {
+		Set<LfsPointer> toPush = findObjectsToPush();
+		if (toPush.isEmpty()) {
+			return EMPTY;
+		}
+		HttpConnection api = LfsConnectionFactory.getLfsConnection(
+				getRepository(), METHOD_POST, OPERATION_UPLOAD);
+		Map<String, LfsPointer> oid2ptr = requestBatchUpload(api, toPush);
+		uploadContents(api, oid2ptr);
+		return EMPTY;
+	}
+
+	private Set<LfsPointer> findObjectsToPush() throws IOException,
+			MissingObjectException, IncorrectObjectTypeException {
+		Set<LfsPointer> toPush = new TreeSet<>();
+
+		try (ObjectWalk walk = new ObjectWalk(getRepository())) {
+			for (RemoteRefUpdate up : refs) {
+				walk.setRewriteParents(false);
+				excludeRemoteRefs(walk);
+				walk.markStart(walk.parseCommit(up.getNewObjectId()));
+				while (walk.next() != null) {
+					// walk all commits to populate objects
+				}
+				findLfsPointers(toPush, walk);
+			}
+		}
+		return toPush;
+	}
+
+	private static void findLfsPointers(Set<LfsPointer> toPush, ObjectWalk walk)
+			throws MissingObjectException, IncorrectObjectTypeException,
+			IOException {
+		RevObject obj;
+		ObjectReader r = walk.getObjectReader();
+		while ((obj = walk.nextObject()) != null) {
+			if (obj.getType() == Constants.OBJ_BLOB
+					&& getObjectSize(r, obj) < LfsPointer.SIZE_THRESHOLD) {
+				LfsPointer ptr = loadLfsPointer(r, obj);
+				if (ptr != null) {
+					toPush.add(ptr);
+				}
+			}
+		}
+	}
+
+	private static long getObjectSize(ObjectReader r, RevObject obj)
+			throws IOException {
+		return r.getObjectSize(obj.getId(), Constants.OBJ_BLOB);
+	}
+
+	private static LfsPointer loadLfsPointer(ObjectReader r, AnyObjectId obj)
+			throws IOException {
+		try (InputStream is = r.open(obj, Constants.OBJ_BLOB).openStream()) {
+			return LfsPointer.parseLfsPointer(is);
+		}
+	}
+
+	private void excludeRemoteRefs(ObjectWalk walk) throws IOException {
+		RefDatabase refDatabase = getRepository().getRefDatabase();
+		Map<String, Ref> remoteRefs = refDatabase.getRefs(remote());
+		for (Ref r : remoteRefs.values()) {
+			ObjectId oid = r.getPeeledObjectId();
+			if (oid == null) {
+				oid = r.getObjectId();
+			}
+			RevObject o = walk.parseAny(oid);
+			if (o.getType() == Constants.OBJ_COMMIT
+					|| o.getType() == Constants.OBJ_TAG) {
+				walk.markUninteresting(o);
+			}
+		}
+	}
+
+	private String remote() {
+		String remoteName = getRemoteName() == null
+				? Constants.DEFAULT_REMOTE_NAME
+				: getRemoteName();
+		return Constants.R_REMOTES + remoteName;
+	}
+
+	private Map<String, LfsPointer> requestBatchUpload(HttpConnection api,
+			Set<LfsPointer> toPush) throws IOException {
+		LfsPointer[] res = toPush.toArray(new LfsPointer[toPush.size()]);
+		Map<String, LfsPointer> oidStr2ptr = new HashMap<>();
+		for (LfsPointer p : res) {
+			oidStr2ptr.put(p.getOid().name(), p);
+		}
+		Gson gson = new Gson();
+		api.getOutputStream().write(
+				gson.toJson(toRequest(OPERATION_UPLOAD, res)).getBytes(UTF_8));
+		int responseCode = api.getResponseCode();
+		if (responseCode != HTTP_OK) {
+			throw new IOException(
+					MessageFormat.format(LfsText.get().serverFailure,
+							api.getURL(), Integer.valueOf(responseCode)));
+		}
+		return oidStr2ptr;
+	}
+
+	private void uploadContents(HttpConnection api,
+			Map<String, LfsPointer> oid2ptr) throws IOException {
+		try (JsonReader reader = new JsonReader(
+				new InputStreamReader(api.getInputStream()))) {
+			for (Protocol.ObjectInfo o : parseObjects(reader)) {
+				if (o.actions == null) {
+					continue;
+				}
+				LfsPointer ptr = oid2ptr.get(o.oid);
+				if (ptr == null) {
+					// received an object we didn't request
+					continue;
+				}
+				Protocol.Action uploadAction = o.actions.get(OPERATION_UPLOAD);
+				if (uploadAction == null || uploadAction.href == null) {
+					continue;
+				}
+
+				Lfs lfs = new Lfs(getRepository());
+				Path path = lfs.getMediaFile(ptr.getOid());
+				if (!Files.exists(path)) {
+					throw new IOException(MessageFormat
+							.format(LfsText.get().missingLocalObject, path));
+				}
+				uploadFile(o, uploadAction, path);
+			}
+		}
+	}
+
+	private List<ObjectInfo> parseObjects(JsonReader reader) {
+		Gson gson = new Gson();
+		Protocol.Response resp = gson.fromJson(reader, Protocol.Response.class);
+		return resp.objects;
+	}
+
+	private void uploadFile(Protocol.ObjectInfo o,
+			Protocol.Action uploadAction, Path path)
+			throws IOException, CorruptMediaFile {
+		HttpConnection contentServer = LfsConnectionFactory
+				.getLfsContentConnection(getRepository(), uploadAction,
+						METHOD_PUT);
+		contentServer.setDoOutput(true);
+		try (OutputStream out = contentServer
+				.getOutputStream()) {
+			long size = Files.copy(path, out);
+			if (size != o.size) {
+				throw new CorruptMediaFile(path, o.size, size);
+			}
+		}
+		int responseCode = contentServer.getResponseCode();
+		if (responseCode != HTTP_OK) {
+			throw new IOException(MessageFormat.format(
+					LfsText.get().serverFailure, contentServer.getURL(),
+					Integer.valueOf(responseCode)));
+		}
+	}
+}
diff --git a/org.eclipse.jgit.lfs/src/org/eclipse/jgit/lfs/SmudgeFilter.java b/org.eclipse.jgit.lfs/src/org/eclipse/jgit/lfs/SmudgeFilter.java
index 841c30a335..1b1b8c1e4a 100644
--- a/org.eclipse.jgit.lfs/src/org/eclipse/jgit/lfs/SmudgeFilter.java
+++ b/org.eclipse.jgit.lfs/src/org/eclipse/jgit/lfs/SmudgeFilter.java
@@ -42,18 +42,10 @@
  */
 package org.eclipse.jgit.lfs;
 
-import static org.eclipse.jgit.util.HttpSupport.ENCODING_GZIP;
-import static org.eclipse.jgit.util.HttpSupport.HDR_ACCEPT;
-import static org.eclipse.jgit.util.HttpSupport.HDR_ACCEPT_ENCODING;
-import static org.eclipse.jgit.util.HttpSupport.HDR_CONTENT_TYPE;
-
-import java.io.BufferedReader;
 import java.io.IOException;
 import java.io.InputStream;
 import java.io.InputStreamReader;
 import java.io.OutputStream;
-import java.net.ProxySelector;
-import java.net.URL;
 import java.nio.charset.StandardCharsets;
 import java.nio.file.Files;
 import java.nio.file.Path;
@@ -61,30 +53,18 @@ import java.text.MessageFormat;
 import java.util.ArrayList;
 import java.util.Collection;
 import java.util.HashMap;
-import java.util.LinkedList;
 import java.util.Map;
-import java.util.TreeMap;
 
 import org.eclipse.jgit.attributes.FilterCommand;
 import org.eclipse.jgit.attributes.FilterCommandFactory;
 import org.eclipse.jgit.attributes.FilterCommandRegistry;
-import org.eclipse.jgit.lfs.errors.LfsConfigInvalidException;
+import org.eclipse.jgit.lfs.internal.LfsConnectionFactory;
 import org.eclipse.jgit.lfs.internal.LfsText;
 import org.eclipse.jgit.lfs.lib.AnyLongObjectId;
 import org.eclipse.jgit.lfs.lib.Constants;
-import org.eclipse.jgit.lib.ConfigConstants;
 import org.eclipse.jgit.lib.Repository;
-import org.eclipse.jgit.lib.StoredConfig;
-import org.eclipse.jgit.transport.HttpConfig;
-import org.eclipse.jgit.transport.HttpTransport;
-import org.eclipse.jgit.transport.RemoteSession;
-import org.eclipse.jgit.transport.SshSessionFactory;
-import org.eclipse.jgit.transport.URIish;
 import org.eclipse.jgit.transport.http.HttpConnection;
-import org.eclipse.jgit.util.FS;
 import org.eclipse.jgit.util.HttpSupport;
-import org.eclipse.jgit.util.io.MessageWriter;
-import org.eclipse.jgit.util.io.StreamCopyThread;
 
 import com.google.gson.Gson;
 import com.google.gson.stream.JsonReader;
@@ -176,11 +156,14 @@ public class SmudgeFilter extends FilterCommand {
 		for (LfsPointer p : res) {
 			oidStr2ptr.put(p.getOid().name(), p);
 		}
-		HttpConnection lfsServerConn = getLfsConnection(db,
-				HttpSupport.METHOD_POST);
+		HttpConnection lfsServerConn = LfsConnectionFactory.getLfsConnection(db,
+				HttpSupport.METHOD_POST, Protocol.OPERATION_DOWNLOAD);
 		Gson gson = new Gson();
 		lfsServerConn.getOutputStream()
-				.write(gson.toJson(body(res)).getBytes(StandardCharsets.UTF_8));
+				.write(gson
+						.toJson(LfsConnectionFactory
+								.toRequest(Protocol.OPERATION_DOWNLOAD, res))
+						.getBytes(StandardCharsets.UTF_8));
 		int responseCode = lfsServerConn.getResponseCode();
 		if (responseCode != HttpConnection.HTTP_OK) {
 			throw new IOException(
@@ -212,21 +195,11 @@ public class SmudgeFilter extends FilterCommand {
 				if (downloadAction == null || downloadAction.href == null) {
 					continue;
 				}
-				URL contentUrl = new URL(downloadAction.href);
-				HttpConnection contentServerConn = HttpTransport
-						.getConnectionFactory().create(contentUrl,
-								HttpSupport.proxyFor(ProxySelector.getDefault(),
-										contentUrl));
-				contentServerConn.setRequestMethod(HttpSupport.METHOD_GET);
-				downloadAction.header.forEach(
-						(k, v) -> contentServerConn.setRequestProperty(k, v));
-				if (contentUrl.getProtocol().equals("https") && !db.getConfig() //$NON-NLS-1$
-						.getBoolean(HttpConfig.HTTP, HttpConfig.SSL_VERIFY_KEY,
-								true)) {
-					HttpSupport.disableSslVerify(contentServerConn);
-				}
-				contentServerConn.setRequestProperty(HDR_ACCEPT_ENCODING,
-						ENCODING_GZIP);
+
+				HttpConnection contentServerConn = LfsConnectionFactory
+						.getLfsContentConnection(db, downloadAction,
+								HttpSupport.METHOD_GET);
+
 				responseCode = contentServerConn.getResponseCode();
 				if (responseCode != HttpConnection.HTTP_OK) {
 					throw new IOException(
@@ -253,148 +226,6 @@ public class SmudgeFilter extends FilterCommand {
 		return downloadedPaths;
 	}
 
-	private Protocol.Request body(LfsPointer... resources) {
-		Protocol.Request req = new Protocol.Request();
-		req.operation = Protocol.OPERATION_DOWNLOAD;
-		if (resources != null) {
-			req.objects = new LinkedList<>();
-			for (LfsPointer res : resources) {
-				Protocol.ObjectSpec o = new Protocol.ObjectSpec();
-				o.oid = res.getOid().getName();
-				o.size = res.getSize();
-				req.objects.add(o);
-			}
-		}
-		return req;
-	}
-
-	/**
-	 * Determine URL of LFS server by looking into config parameters lfs.url,
-	 * lfs.<remote>.url or remote.<remote>.url. The LFS server URL is computed
-	 * from remote.<remote>.url by appending "/info/lfs"
-	 *
-	 * @param db
-	 *            the repository to work with
-	 * @param method
-	 *            the method (GET,PUT,...) of the request this connection will
-	 *            be used for
-	 * @return the url for the lfs server. e.g.
-	 *         "https://github.com/github/git-lfs.git/info/lfs"
-	 * @throws IOException
-	 */
-	private HttpConnection getLfsConnection(Repository db, String method)
-			throws IOException {
-		StoredConfig config = db.getConfig();
-		String lfsEndpoint = config.getString(Constants.LFS, null,
-				ConfigConstants.CONFIG_KEY_URL);
-		Map<String, String> additionalHeaders = new TreeMap<>();
-		if (lfsEndpoint == null) {
-			String remoteUrl = null;
-			for (String remote : db.getRemoteNames()) {
-				lfsEndpoint = config.getString(Constants.LFS, remote,
-						ConfigConstants.CONFIG_KEY_URL);
-				if (lfsEndpoint == null
-						&& (remote.equals(
-								org.eclipse.jgit.lib.Constants.DEFAULT_REMOTE_NAME))) {
-					remoteUrl = config.getString(
-							ConfigConstants.CONFIG_KEY_REMOTE, remote,
-							ConfigConstants.CONFIG_KEY_URL);
-				}
-				break;
-			}
-			if (lfsEndpoint == null && remoteUrl != null) {
-				try {
-					URIish u = new URIish(remoteUrl);
-
-					if ("ssh".equals(u.getScheme())) { //$NON-NLS-1$
-						// discover and authenticate; git-lfs does "ssh -p
-						// <port> -- <host> git-lfs-authenticate <project>
-						// <upload/download>"
-						String json = runSshCommand(u.setPath(""), db.getFS(), //$NON-NLS-1$
-								"git-lfs-authenticate " + extractProjectName(u) //$NON-NLS-1$
-										+ " " + Protocol.OPERATION_DOWNLOAD); //$NON-NLS-1$
-
-						Protocol.Action action = new Gson().fromJson(json,
-								Protocol.Action.class);
-						additionalHeaders.putAll(action.header);
-						lfsEndpoint = action.href;
-					} else {
-						lfsEndpoint = remoteUrl + Protocol.INFO_LFS_ENDPOINT;
-					}
-				} catch (Exception e) {
-					lfsEndpoint = null; // could not discover
-				}
-			} else {
-				lfsEndpoint = lfsEndpoint + Protocol.INFO_LFS_ENDPOINT;
-			}
-		}
-		if (lfsEndpoint == null) {
-			throw new LfsConfigInvalidException(LfsText.get().lfsNoDownloadUrl);
-		}
-		URL url = new URL(lfsEndpoint + Protocol.OBJECTS_LFS_ENDPOINT);
-		HttpConnection connection = HttpTransport.getConnectionFactory().create(
-				url, HttpSupport.proxyFor(ProxySelector.getDefault(), url));
-		connection.setDoOutput(true);
-		if (url.getProtocol().equals("https") //$NON-NLS-1$
-				&& !config.getBoolean(HttpConfig.HTTP,
-						HttpConfig.SSL_VERIFY_KEY, true)) {
-			HttpSupport.disableSslVerify(connection);
-		}
-		connection.setRequestMethod(method);
-		connection.setRequestProperty(HDR_ACCEPT,
-				Protocol.CONTENTTYPE_VND_GIT_LFS_JSON);
-		connection.setRequestProperty(HDR_CONTENT_TYPE,
-				Protocol.CONTENTTYPE_VND_GIT_LFS_JSON);
-		additionalHeaders
-				.forEach((k, v) -> connection.setRequestProperty(k, v));
-		return connection;
-	}
-
-	private String extractProjectName(URIish u) {
-		String path = u.getPath().substring(1);
-		if (path.endsWith(org.eclipse.jgit.lib.Constants.DOT_GIT)) {
-			return path.substring(0, path.length() - 4);
-		} else {
-			return path;
-		}
-	}
-
-	private String runSshCommand(URIish sshUri, FS fs, String command)
-			throws IOException {
-		RemoteSession session = null;
-		Process process = null;
-		StreamCopyThread errorThread = null;
-		try (MessageWriter stderr = new MessageWriter()) {
-			session = SshSessionFactory.getInstance().getSession(sshUri,
-					null, fs, 5_000);
-			process = session.exec(command, 0);
-			errorThread = new StreamCopyThread(process.getErrorStream(),
-					stderr.getRawStream());
-			errorThread.start();
-			try (BufferedReader reader = new BufferedReader(
-					new InputStreamReader(process.getInputStream(),
-							org.eclipse.jgit.lib.Constants.CHARSET))) {
-				return reader.readLine();
-			}
-		} finally {
-			if (process != null) {
-				process.destroy();
-			}
-			if (errorThread != null) {
-				try {
-					errorThread.halt();
-				} catch (InterruptedException e) {
-					// Stop waiting and return anyway.
-				} finally {
-					errorThread = null;
-				}
-			}
-			if (session != null) {
-				SshSessionFactory.getInstance().releaseSession(session);
-			}
-		}
-	}
-
 	/** {@inheritDoc} */
 	@Override
 	public int run() throws IOException {
diff --git a/org.eclipse.jgit.lfs/src/org/eclipse/jgit/lfs/internal/LfsConnectionFactory.java b/org.eclipse.jgit.lfs/src/org/eclipse/jgit/lfs/internal/LfsConnectionFactory.java
new file mode 100644
index 0000000000..254bd5ae05
--- /dev/null
+++ b/org.eclipse.jgit.lfs/src/org/eclipse/jgit/lfs/internal/LfsConnectionFactory.java
@@ -0,0 +1,294 @@
+/*
+ * Copyright (C) 2017, Markus Duft <markus.duft@ssi-schaefer.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.internal;
+
+import static org.eclipse.jgit.util.HttpSupport.ENCODING_GZIP;
+import static org.eclipse.jgit.util.HttpSupport.HDR_ACCEPT;
+import static org.eclipse.jgit.util.HttpSupport.HDR_ACCEPT_ENCODING;
+import static org.eclipse.jgit.util.HttpSupport.HDR_CONTENT_TYPE;
+
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.InputStreamReader;
+import java.net.ProxySelector;
+import java.net.URL;
+import java.util.LinkedList;
+import java.util.Map;
+import java.util.TreeMap;
+
+import org.eclipse.jgit.annotations.NonNull;
+import org.eclipse.jgit.lfs.LfsPointer;
+import org.eclipse.jgit.lfs.Protocol;
+import org.eclipse.jgit.lfs.errors.LfsConfigInvalidException;
+import org.eclipse.jgit.lfs.lib.Constants;
+import org.eclipse.jgit.lib.ConfigConstants;
+import org.eclipse.jgit.lib.Repository;
+import org.eclipse.jgit.lib.StoredConfig;
+import org.eclipse.jgit.transport.HttpConfig;
+import org.eclipse.jgit.transport.HttpTransport;
+import org.eclipse.jgit.transport.RemoteSession;
+import org.eclipse.jgit.transport.SshSessionFactory;
+import org.eclipse.jgit.transport.URIish;
+import org.eclipse.jgit.transport.http.HttpConnection;
+import org.eclipse.jgit.util.FS;
+import org.eclipse.jgit.util.HttpSupport;
+import org.eclipse.jgit.util.io.MessageWriter;
+import org.eclipse.jgit.util.io.StreamCopyThread;
+
+import com.google.gson.Gson;
+
+/**
+ * Provides means to get a valid LFS connection for a given repository.
+ */
+public class LfsConnectionFactory {
+
+	private static final String SCHEME_HTTPS = "https"; //$NON-NLS-1$
+	private static final String SCHEME_SSH = "ssh"; //$NON-NLS-1$
+
+	/**
+	 * Determine URL of LFS server by looking into config parameters lfs.url,
+	 * lfs.[remote].url or remote.[remote].url. The LFS server URL is computed
+	 * from remote.[remote].url by appending "/info/lfs". In case there is no
+	 * URL configured, a SSH remote URI can be used to auto-detect the LFS URI
+	 * by using the remote "git-lfs-authenticate" command.
+	 *
+	 * @param db
+	 *            the repository to work with
+	 * @param method
+	 *            the method (GET,PUT,...) of the request this connection will
+	 *            be used for
+	 * @param purpose
+	 *            the action, e.g. Protocol.OPERATION_DOWNLOAD
+	 * @return the url for the lfs server. e.g.
+	 *         "https://github.com/github/git-lfs.git/info/lfs"
+	 * @throws IOException
+	 */
+	public static HttpConnection getLfsConnection(Repository db, String method,
+			String purpose) throws IOException {
+		StoredConfig config = db.getConfig();
+		Map<String, String> additionalHeaders = new TreeMap<>();
+		String lfsUrl = getLfsUrl(db, purpose, additionalHeaders);
+		URL url = new URL(lfsUrl + Protocol.OBJECTS_LFS_ENDPOINT);
+		HttpConnection connection = HttpTransport.getConnectionFactory().create(
+				url, HttpSupport.proxyFor(ProxySelector.getDefault(), url));
+		connection.setDoOutput(true);
+		if (url.getProtocol().equals(SCHEME_HTTPS)
+				&& !config.getBoolean(HttpConfig.HTTP,
+						HttpConfig.SSL_VERIFY_KEY, true)) {
+			HttpSupport.disableSslVerify(connection);
+		}
+		connection.setRequestMethod(method);
+		connection.setRequestProperty(HDR_ACCEPT,
+				Protocol.CONTENTTYPE_VND_GIT_LFS_JSON);
+		connection.setRequestProperty(HDR_CONTENT_TYPE,
+				Protocol.CONTENTTYPE_VND_GIT_LFS_JSON);
+		additionalHeaders
+				.forEach((k, v) -> connection.setRequestProperty(k, v));
+		return connection;
+	}
+
+	private static String getLfsUrl(Repository db, String purpose,
+			Map<String, String> additionalHeaders)
+			throws LfsConfigInvalidException {
+		StoredConfig config = db.getConfig();
+		String lfsUrl = config.getString(Constants.LFS, null,
+				ConfigConstants.CONFIG_KEY_URL);
+		if (lfsUrl == null) {
+			String remoteUrl = null;
+			for (String remote : db.getRemoteNames()) {
+				lfsUrl = config.getString(Constants.LFS, remote,
+						ConfigConstants.CONFIG_KEY_URL);
+				// This could be done better (more precise logic), but according
+				// to https://github.com/git-lfs/git-lfs/issues/1759 git-lfs
+				// generally only supports 'origin' in an integrated workflow.
+				if (lfsUrl == null && (remote.equals(
+						org.eclipse.jgit.lib.Constants.DEFAULT_REMOTE_NAME))) {
+					remoteUrl = config.getString(
+							ConfigConstants.CONFIG_KEY_REMOTE, remote,
+							ConfigConstants.CONFIG_KEY_URL);
+				}
+				break;
+			}
+			if (lfsUrl == null && remoteUrl != null) {
+				lfsUrl = discoverLfsUrl(db, purpose, additionalHeaders,
+						remoteUrl);
+			} else {
+				lfsUrl = lfsUrl + Protocol.INFO_LFS_ENDPOINT;
+			}
+		}
+		if (lfsUrl == null) {
+			throw new LfsConfigInvalidException(LfsText.get().lfsNoDownloadUrl);
+		}
+		return lfsUrl;
+	}
+
+	private static String discoverLfsUrl(Repository db, String purpose,
+			Map<String, String> additionalHeaders, String remoteUrl) {
+		try {
+			URIish u = new URIish(remoteUrl);
+
+			if (SCHEME_SSH.equals(u.getScheme())) {
+				// discover and authenticate; git-lfs does "ssh -p
+				// <port> -- <host> git-lfs-authenticate <project>
+				// <upload/download>"
+				String json = runSshCommand(u.setPath(""), db.getFS(), //$NON-NLS-1$
+						"git-lfs-authenticate " + extractProjectName(u) //$NON-NLS-1$
+								+ " " + purpose); //$NON-NLS-1$
+
+				Protocol.Action action = new Gson().fromJson(json,
+						Protocol.Action.class);
+				additionalHeaders.putAll(action.header);
+				return action.href;
+			} else {
+				return remoteUrl + Protocol.INFO_LFS_ENDPOINT;
+			}
+		} catch (Exception e) {
+			return null; // could not discover
+		}
+	}
+
+	/**
+	 * Create a connection for the specified
+	 * {@link org.eclipse.jgit.lfs.Protocol.Action}.
+	 *
+	 * @param repo
+	 *            the repo to fetch required configuration from
+	 * @param action
+	 *            the action for which to create a connection
+	 * @param method
+	 *            the target method (GET or PUT)
+	 * @return a connection. output mode is not set.
+	 * @throws IOException
+	 *             in case of any error.
+	 */
+	public static @NonNull HttpConnection getLfsContentConnection(
+			Repository repo, Protocol.Action action, String method)
+			throws IOException {
+		URL contentUrl = new URL(action.href);
+		HttpConnection contentServerConn = HttpTransport.getConnectionFactory()
+				.create(contentUrl, HttpSupport
+						.proxyFor(ProxySelector.getDefault(), contentUrl));
+		contentServerConn.setRequestMethod(method);
+		action.header
+				.forEach((k, v) -> contentServerConn.setRequestProperty(k, v));
+		if (contentUrl.getProtocol().equals(SCHEME_HTTPS)
+				&& !repo.getConfig().getBoolean(HttpConfig.HTTP,
+						HttpConfig.SSL_VERIFY_KEY, true)) {
+			HttpSupport.disableSslVerify(contentServerConn);
+		}
+
+		contentServerConn.setRequestProperty(HDR_ACCEPT_ENCODING,
+				ENCODING_GZIP);
+
+		return contentServerConn;
+	}
+
+	private static String extractProjectName(URIish u) {
+		String path = u.getPath().substring(1);
+		if (path.endsWith(org.eclipse.jgit.lib.Constants.DOT_GIT)) {
+			return path.substring(0, path.length() - 4);
+		} else {
+			return path;
+		}
+	}
+
+	private static String runSshCommand(URIish sshUri, FS fs, String command)
+			throws IOException {
+		RemoteSession session = null;
+		Process process = null;
+		StreamCopyThread errorThread = null;
+		try (MessageWriter stderr = new MessageWriter()) {
+			session = SshSessionFactory.getInstance().getSession(sshUri, null,
+					fs, 5_000);
+			process = session.exec(command, 0);
+			errorThread = new StreamCopyThread(process.getErrorStream(),
+					stderr.getRawStream());
+			errorThread.start();
+			try (BufferedReader reader = new BufferedReader(
+					new InputStreamReader(process.getInputStream(),
+							org.eclipse.jgit.lib.Constants.CHARSET))) {
+				return reader.readLine();
+			}
+		} finally {
+			if (process != null) {
+				process.destroy();
+			}
+			if (errorThread != null) {
+				try {
+					errorThread.halt();
+				} catch (InterruptedException e) {
+					// Stop waiting and return anyway.
+				} finally {
+					errorThread = null;
+				}
+			}
+			if (session != null) {
+				SshSessionFactory.getInstance().releaseSession(session);
+			}
+		}
+	}
+
+	/**
+	 * @param operation
+	 *            the operation to perform, e.g. Protocol.OPERATION_DOWNLOAD
+	 * @param resources
+	 *            the LFS resources affected
+	 * @return a request that can be serialized to JSON
+	 */
+	public static Protocol.Request toRequest(String operation,
+			LfsPointer... resources) {
+		Protocol.Request req = new Protocol.Request();
+		req.operation = operation;
+		if (resources != null) {
+			req.objects = new LinkedList<>();
+			for (LfsPointer res : resources) {
+				Protocol.ObjectSpec o = new Protocol.ObjectSpec();
+				o.oid = res.getOid().getName();
+				o.size = res.getSize();
+				req.objects.add(o);
+			}
+		}
+		return req;
+	}
+
+}
diff --git a/org.eclipse.jgit.lfs/src/org/eclipse/jgit/lfs/internal/LfsText.java b/org.eclipse.jgit.lfs/src/org/eclipse/jgit/lfs/internal/LfsText.java
index 8fc2b1bef5..d82ade2f7f 100644
--- a/org.eclipse.jgit.lfs/src/org/eclipse/jgit/lfs/internal/LfsText.java
+++ b/org.eclipse.jgit.lfs/src/org/eclipse/jgit/lfs/internal/LfsText.java
@@ -76,4 +76,5 @@ public class LfsText extends TranslationBundle {
 	/***/ public String serverFailure;
 	/***/ public String wrongAmoutOfDataReceived;
 	/***/ public String userConfigInvalid;
+	/***/ public String missingLocalObject;
 }