Implement server support for shallow clones

This implements the server side of shallow clones only (i.e.
git-upload-pack), not the client side.

CQ: 5517
Bug: 301627
Change-Id: Ied5f501f9c8d1fe90ab2ba44fac5fa67ed0035a4
Signed-off-by: Chris Aniszczyk <caniszczyk@gmail.com>

org.eclipse.jgit/src/org/eclipse/jgit/revwalk/DepthGenerator.java

@@ -0,0 +1,176 @@
+/*
+ * Copyright (C) 2010, Garmin International
+ * Copyright (C) 2010, Matt Fischer <matt.fischer@garmin.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.revwalk;
+
+import java.io.IOException;
+
+import org.eclipse.jgit.errors.IncorrectObjectTypeException;
+import org.eclipse.jgit.errors.MissingObjectException;
+
+/**
+ * Only produce commits which are below a specified depth.
+ *
+ * @see DepthWalk
+ */
+class DepthGenerator extends Generator {
+	private final FIFORevQueue pending;
+
+	private final int depth;
+
+	private final RevWalk walk;
+
+	/**
+	 * Commits which used to be shallow in the client, but which are
+	 * being extended as part of this fetch.  These commits should be
+	 * returned to the caller as UNINTERESTING so that their blobs/trees
+	 * can be marked appropriately in the pack writer.
+	 */
+	private final RevFlag UNSHALLOW;
+
+	/**
+	 * Commits which the normal framework has marked as UNINTERESTING,
+	 * but which we now care about again.  This happens if a client is
+	 * extending a shallow checkout to become deeper--the new commits at
+	 * the bottom of the graph need to be sent, even though they are
+	 * below other commits which the client already has.
+	 */
+	private final RevFlag REINTERESTING;
+
+	/**
+	 * @param w
+	 * @param s Parent generator
+	 * @throws MissingObjectException
+	 * @throws IncorrectObjectTypeException
+	 * @throws IOException
+	 */
+	DepthGenerator(DepthWalk w, Generator s) throws MissingObjectException,
+			IncorrectObjectTypeException, IOException {
+		pending = new FIFORevQueue();
+		walk = (RevWalk)w;
+
+		this.depth = w.getDepth();
+		this.UNSHALLOW = w.getUnshallowFlag();
+		this.REINTERESTING = w.getReinterestingFlag();
+
+		s.shareFreeList(pending);
+
+		// Begin by sucking out all of the source's commits, and
+		// adding them to the pending queue
+		for (;;) {
+			RevCommit c = s.next();
+			if (c == null)
+				break;
+			if (((DepthWalk.Commit) c).getDepth() == 0)
+				pending.add(c);
+		}
+	}
+
+	@Override
+	int outputType() {
+		return pending.outputType() | HAS_UNINTERESTING;
+	}
+
+	@Override
+	void shareFreeList(final BlockRevQueue q) {
+		pending.shareFreeList(q);
+	}
+
+	@Override
+	RevCommit next() throws MissingObjectException,
+			IncorrectObjectTypeException, IOException {
+		// Perform a breadth-first descent into the commit graph,
+		// marking depths as we go.  This means that if a commit is
+		// reachable by more than one route, we are guaranteed to
+		// arrive by the shortest route first.
+		for (;;) {
+			final DepthWalk.Commit c = (DepthWalk.Commit) pending.next();
+			if (c == null)
+				return null;
+
+			if ((c.flags & RevWalk.PARSED) == 0)
+				c.parseHeaders(walk);
+
+			int newDepth = c.depth + 1;
+
+			for (final RevCommit p : c.parents) {
+				DepthWalk.Commit dp = (DepthWalk.Commit) p;
+
+				// If no depth has been assigned to this commit, assign
+				// it now.  Since we arrive by the shortest route first,
+				// this depth is guaranteed to be the smallest value that
+				// any path could produce.
+				if (dp.depth == -1) {
+					dp.depth = newDepth;
+
+					// If the parent is not too deep, add it to the queue
+					// so that we can produce it later
+					if (newDepth <= depth)
+						pending.add(p);
+				}
+
+				// If the current commit has become unshallowed, everything
+				// below us is new to the client.  Mark its parent as
+				// re-interesting, and carry that flag downward to all
+				// of its ancestors.
+				if(c.has(UNSHALLOW) || c.has(REINTERESTING)) {
+					p.add(REINTERESTING);
+					p.flags &= ~RevWalk.UNINTERESTING;
+				}
+			}
+
+			// Produce all commits less than the depth cutoff
+			boolean produce = c.depth <= depth;
+
+			// Unshallow commits are uninteresting, but still need to be sent
+			// up to the PackWriter so that it will exclude objects correctly.
+			// All other uninteresting commits should be omitted.
+			if ((c.flags & RevWalk.UNINTERESTING) != 0 && !c.has(UNSHALLOW))
+				produce = false;
+
+			if (produce)
+				return c;
+		}
+	}
+}

org.eclipse.jgit/src/org/eclipse/jgit/revwalk/DepthWalk.java

@@ -0,0 +1,243 @@
+/*
+ * Copyright (C) 2010, Garmin International
+ * Copyright (C) 2010, Matt Fischer <matt.fischer@garmin.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.revwalk;
+
+import java.io.IOException;
+
+import org.eclipse.jgit.errors.IncorrectObjectTypeException;
+import org.eclipse.jgit.errors.MissingObjectException;
+import org.eclipse.jgit.lib.AnyObjectId;
+import org.eclipse.jgit.lib.ObjectReader;
+import org.eclipse.jgit.lib.Repository;
+
+/** Interface for revision walkers that perform depth filtering. */
+public interface DepthWalk {
+	/** @return Depth to filter to. */
+	public int getDepth();
+
+	/** @return flag marking commits that should become unshallow. */
+	public RevFlag getUnshallowFlag();
+
+	/** @return flag marking commits that are interesting again. */
+	public RevFlag getReinterestingFlag();
+
+	/** RevCommit with a depth (in commits) from a root. */
+	public static class Commit extends RevCommit {
+		/** Depth of this commit in the graph, via shortest path. */
+		int depth;
+
+		/** @return depth of this commit, as found by the shortest path. */
+		public int getDepth() {
+			return depth;
+		}
+
+		/**
+		 * Initialize a new commit.
+		 *
+		 * @param id
+		 *            object name for the commit.
+		 */
+		protected Commit(AnyObjectId id) {
+			super(id);
+			depth = -1;
+		}
+	}
+
+	/** Subclass of RevWalk that performs depth filtering. */
+	public class RevWalk extends org.eclipse.jgit.revwalk.RevWalk implements DepthWalk {
+		private final int depth;
+
+		private final RevFlag UNSHALLOW;
+
+		private final RevFlag REINTERESTING;
+
+		/**
+		 * @param repo Repository to walk
+		 * @param depth Maximum depth to return
+		 */
+		public RevWalk(Repository repo, int depth) {
+			super(repo);
+
+			this.depth = depth;
+			this.UNSHALLOW = newFlag("UNSHALLOW");
+			this.REINTERESTING = newFlag("REINTERESTING");
+		}
+
+		/**
+		 * @param or ObjectReader to use
+		 * @param depth Maximum depth to return
+		 */
+		public RevWalk(ObjectReader or, int depth) {
+			super(or);
+
+			this.depth = depth;
+			this.UNSHALLOW = newFlag("UNSHALLOW");
+			this.REINTERESTING = newFlag("REINTERESTING");
+		}
+
+		/**
+		 * Mark a root commit (i.e., one whose depth should be considered 0.)
+		 *
+		 * @param c
+		 *            Commit to mark
+		 * @throws IOException
+		 * @throws IncorrectObjectTypeException
+		 * @throws MissingObjectException
+		 */
+		public void markRoot(RevCommit c) throws MissingObjectException,
+				IncorrectObjectTypeException, IOException {
+			if (c instanceof Commit)
+				((Commit) c).depth = 0;
+			super.markStart(c);
+		}
+
+		@Override
+		protected RevCommit createCommit(AnyObjectId id) {
+			return new Commit(id);
+		}
+
+		public int getDepth() {
+			return depth;
+		}
+
+		public RevFlag getUnshallowFlag() {
+			return UNSHALLOW;
+		}
+
+		public RevFlag getReinterestingFlag() {
+			return REINTERESTING;
+		}
+	}
+
+	/** Subclass of ObjectWalk that performs depth filtering. */
+	public class ObjectWalk extends org.eclipse.jgit.revwalk.ObjectWalk implements DepthWalk {
+		private final int depth;
+
+		private final RevFlag UNSHALLOW;
+
+		private final RevFlag REINTERESTING;
+
+		/**
+		 * @param repo Repository to walk
+		 * @param depth Maximum depth to return
+		 */
+		public ObjectWalk(Repository repo, int depth) {
+			super(repo);
+
+			this.depth = depth;
+			this.UNSHALLOW = newFlag("UNSHALLOW");
+			this.REINTERESTING = newFlag("REINTERESTING");
+		}
+
+		/**
+		 * @param or Object Reader
+		 * @param depth Maximum depth to return
+		 */
+		public ObjectWalk(ObjectReader or, int depth) {
+			super(or);
+
+			this.depth = depth;
+			this.UNSHALLOW = newFlag("UNSHALLOW");
+			this.REINTERESTING = newFlag("REINTERESTING");
+		}
+
+		/**
+		 * Mark a root commit (i.e., one whose depth should be considered 0.)
+		 *
+		 * @param o
+		 *            Commit to mark
+		 * @throws IOException
+		 * @throws IncorrectObjectTypeException
+		 * @throws MissingObjectException
+		 */
+		public void markRoot(RevObject o) throws MissingObjectException,
+				IncorrectObjectTypeException, IOException {
+			RevObject c = o;
+			while (c instanceof RevTag) {
+				c = ((RevTag) c).getObject();
+				parseHeaders(c);
+			}
+			if (c instanceof Commit)
+				((Commit) c).depth = 0;
+			super.markStart(o);
+		}
+
+		/**
+		 * Mark an element which used to be shallow in the client, but which
+		 * should now be considered a full commit. Any ancestors of this commit
+		 * should be included in the walk, even if they are the ancestor of an
+		 * uninteresting commit.
+		 *
+		 * @param c
+		 *            Commit to mark
+		 * @throws MissingObjectException
+		 * @throws IncorrectObjectTypeException
+		 * @throws IOException
+		 */
+		public void markUnshallow(RevObject c) throws MissingObjectException,
+				IncorrectObjectTypeException, IOException {
+			if (c instanceof RevCommit)
+				c.add(UNSHALLOW);
+			super.markStart(c);
+		}
+
+		@Override
+		protected RevCommit createCommit(AnyObjectId id) {
+			return new Commit(id);
+		}
+
+		public int getDepth() {
+			return depth;
+		}
+
+		public RevFlag getUnshallowFlag() {
+			return UNSHALLOW;
+		}
+
+		public RevFlag getReinterestingFlag() {
+			return REINTERESTING;
+		}
+	}
+}

org.eclipse.jgit/src/org/eclipse/jgit/revwalk/StartGenerator.java

@@ -132,14 +132,20 @@ class StartGenerator extends Generator {
 		}
 
 		walker.queue = q;
-		g = new PendingGenerator(w, pending, rf, pendingOutputType);
 
-		if (boundary) {
-			// Because the boundary generator may produce uninteresting
-			// commits we cannot allow the pending generator to dispose
-			// of them early.
-			//
-			((PendingGenerator) g).canDispose = false;
+		if (walker instanceof DepthWalk) {
+			DepthWalk dw = (DepthWalk) walker;
+			g = new DepthGenerator(dw, pending);
+		} else {
+			g = new PendingGenerator(w, pending, rf, pendingOutputType);
+
+			if (boundary) {
+				// Because the boundary generator may produce uninteresting
+				// commits we cannot allow the pending generator to dispose
+				// of them early.
+				//
+				((PendingGenerator) g).canDispose = false;
+			}
 		}
 
 		if ((g.outputType() & NEEDS_REWRITE) != 0) {

org.eclipse.jgit/src/org/eclipse/jgit/storage/pack/PackWriter.java

@@ -91,6 +91,7 @@ import org.eclipse.jgit.lib.ProgressMonitor;
 import org.eclipse.jgit.lib.Repository;
 import org.eclipse.jgit.lib.ThreadSafeProgressMonitor;
 import org.eclipse.jgit.revwalk.AsyncRevObjectQueue;
+import org.eclipse.jgit.revwalk.DepthWalk;
 import org.eclipse.jgit.revwalk.ObjectWalk;
 import org.eclipse.jgit.revwalk.RevCommit;
 import org.eclipse.jgit.revwalk.RevFlag;
@@ -195,6 +196,12 @@ public class PackWriter {
 
 	private boolean pruneCurrentObjectList;
 
+	private boolean shallowPack;
+
+	private int depth;
+
+	private Collection<? extends ObjectId> unshallowObjects;
+
 	/**
 	 * Create writer for specified repository.
 	 * <p>
@@ -407,6 +414,22 @@ public class PackWriter {
 		tagTargets = objects;
 	}
 
+	/**
+	 * Configure this pack for a shallow clone.
+	 *
+	 * @param depth
+	 *            maximum depth to traverse the commit graph
+	 * @param unshallow
+	 *            objects which used to be shallow on the client, but are being
+	 *            extended as part of this fetch
+	 */
+	public void setShallowPack(int depth,
+			Collection<? extends ObjectId> unshallow) {
+		this.shallowPack = true;
+		this.depth = depth;
+		this.unshallowObjects = unshallow;
+	}
+
 	/**
 	 * Returns objects number in a pack file that was created by this writer.
 	 *
@@ -538,7 +561,7 @@ public class PackWriter {
 	 */
 	@Deprecated
 	public void preparePack(ProgressMonitor countingMonitor,
-			final ObjectWalk walk,
+			ObjectWalk walk,
 			final Collection<? extends ObjectId> interestingObjects,
 			final Collection<? extends ObjectId> uninterestingObjects)
 			throws IOException {
@@ -585,7 +608,11 @@ public class PackWriter {
 	public void preparePack(ProgressMonitor countingMonitor,
 			Set<? extends ObjectId> want,
 			Set<? extends ObjectId> have) throws IOException {
-		ObjectWalk ow = new ObjectWalk(reader);
+		ObjectWalk ow;
+		if (shallowPack)
+			ow = new DepthWalk.ObjectWalk(reader, depth);
+		else
+			ow = new ObjectWalk(reader);
 		preparePack(countingMonitor, ow, want, have);
 	}
 
@@ -615,12 +642,14 @@ public class PackWriter {
 	 *             when some I/O problem occur during reading objects.
 	 */
 	public void preparePack(ProgressMonitor countingMonitor,
-			final ObjectWalk walk,
+			ObjectWalk walk,
 			final Set<? extends ObjectId> interestingObjects,
 			final Set<? extends ObjectId> uninterestingObjects)
 			throws IOException {
 		if (countingMonitor == null)
 			countingMonitor = NullProgressMonitor.INSTANCE;
+		if (shallowPack && !(walk instanceof DepthWalk.ObjectWalk))
+			walk = new DepthWalk.ObjectWalk(reader, depth);
 		findObjectsToPack(countingMonitor, walk, interestingObjects,
 				uninterestingObjects);
 	}
@@ -1443,9 +1472,9 @@ public class PackWriter {
 					if (tipToPack.containsKey(o))
 						o.add(inCachedPack);
 
-					if (have.contains(o)) {
+					if (have.contains(o))
 						haveObjs.add(o);
-					} else if (want.contains(o)) {
+					if (want.contains(o)) {
 						o.add(include);
 						wantObjs.add(o);
 						if (o instanceof RevTag)
@@ -1476,8 +1505,18 @@ public class PackWriter {
 			}
 		}
 
-		for (RevObject obj : wantObjs)
-			walker.markStart(obj);
+		if (walker instanceof DepthWalk.ObjectWalk) {
+			DepthWalk.ObjectWalk depthWalk = (DepthWalk.ObjectWalk) walker;
+			for (RevObject obj : wantObjs)
+				depthWalk.markRoot(obj);
+			if (unshallowObjects != null) {
+				for (ObjectId id : unshallowObjects)
+					depthWalk.markUnshallow(walker.parseAny(id));
+			}
+		} else {
+			for (RevObject obj : wantObjs)
+				walker.markStart(obj);
+		}
 		for (RevObject obj : haveObjs)
 			walker.markUninteresting(obj);
 
@@ -1512,36 +1551,42 @@ public class PackWriter {
 			countingMonitor.update(1);
 		}
 
-		int commitCnt = 0;
-		boolean putTagTargets = false;
-		for (RevCommit cmit : commits) {
-			if (!cmit.has(added)) {
-				cmit.add(added);
+		if (shallowPack) {
+			for (RevCommit cmit : commits) {
 				addObject(cmit, 0);
-				commitCnt++;
 			}
-
-			for (int i = 0; i < cmit.getParentCount(); i++) {
-				RevCommit p = cmit.getParent(i);
-				if (!p.has(added) && !p.has(RevFlag.UNINTERESTING)) {
-					p.add(added);
-					addObject(p, 0);
+		} else {
+			int commitCnt = 0;
+			boolean putTagTargets = false;
+			for (RevCommit cmit : commits) {
+				if (!cmit.has(added)) {
+					cmit.add(added);
+					addObject(cmit, 0);
 					commitCnt++;
 				}
-			}
 
-			if (!putTagTargets && 4096 < commitCnt) {
-				for (ObjectId id : tagTargets) {
-					RevObject obj = walker.lookupOrNull(id);
-					if (obj instanceof RevCommit
-							&& obj.has(include)
-							&& !obj.has(RevFlag.UNINTERESTING)
-							&& !obj.has(added)) {
-						obj.add(added);
-						addObject(obj, 0);
+				for (int i = 0; i < cmit.getParentCount(); i++) {
+					RevCommit p = cmit.getParent(i);
+					if (!p.has(added) && !p.has(RevFlag.UNINTERESTING)) {
+						p.add(added);
+						addObject(p, 0);
+						commitCnt++;
+					}
+				}
+
+				if (!putTagTargets && 4096 < commitCnt) {
+					for (ObjectId id : tagTargets) {
+						RevObject obj = walker.lookupOrNull(id);
+						if (obj instanceof RevCommit
+								&& obj.has(include)
+								&& !obj.has(RevFlag.UNINTERESTING)
+								&& !obj.has(added)) {
+							obj.add(added);
+							addObject(obj, 0);
+						}
 					}
+					putTagTargets = true;
 				}
-				putTagTargets = true;
 			}
 		}
 		commits = null;

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

@@ -56,6 +56,7 @@ import java.util.Set;
 
 import org.eclipse.jgit.JGitText;
 import org.eclipse.jgit.errors.CorruptObjectException;
+import org.eclipse.jgit.errors.IncorrectObjectTypeException;
 import org.eclipse.jgit.errors.MissingObjectException;
 import org.eclipse.jgit.errors.PackProtocolException;
 import org.eclipse.jgit.lib.Constants;
@@ -65,6 +66,7 @@ import org.eclipse.jgit.lib.ProgressMonitor;
 import org.eclipse.jgit.lib.Ref;
 import org.eclipse.jgit.lib.Repository;
 import org.eclipse.jgit.revwalk.AsyncRevObjectQueue;
+import org.eclipse.jgit.revwalk.DepthWalk;
 import org.eclipse.jgit.revwalk.ObjectWalk;
 import org.eclipse.jgit.revwalk.RevCommit;
 import org.eclipse.jgit.revwalk.RevFlag;
@@ -103,6 +105,8 @@ public class UploadPack {
 
 	static final String OPTION_NO_DONE = BasePackFetchConnection.OPTION_NO_DONE;
 
+	static final String OPTION_SHALLOW = BasePackFetchConnection.OPTION_SHALLOW;
+
 	/** Database we read the objects from. */
 	private final Repository db;
 
@@ -160,6 +164,15 @@ public class UploadPack {
 	/** Objects on both sides, these don't have to be sent. */
 	private final Set<RevObject> commonBase = new HashSet<RevObject>();
 
+	/** Shallow commits the client already has. */
+	private final Set<ObjectId> clientShallowCommits = new HashSet<ObjectId>();
+
+	/** Shallow commits on the client which are now becoming unshallow */
+	private final List<ObjectId> unshallowCommits = new ArrayList<ObjectId>();
+
+	/** Desired depth from the client on a shallow request. */
+	private int depth;
+
 	/** Commit time of the oldest common commit, in seconds. */
 	private int oldestTime;
 
@@ -418,6 +431,8 @@ public class UploadPack {
 			else
 				multiAck = MultiAck.OFF;
 
+			if (depth != 0)
+				processShallow();
 			sendPack = negotiate();
 		} catch (PackProtocolException err) {
 			reportErrorDuringNegotiate(err.getMessage());
@@ -457,6 +472,39 @@ public class UploadPack {
 		}
 	}
 
+	private void processShallow() throws IOException {
+		DepthWalk.RevWalk depthWalk =
+			new DepthWalk.RevWalk(walk.getObjectReader(), depth);
+
+		// Find all the commits which will be shallow
+		for (ObjectId o : wantIds) {
+			try {
+				depthWalk.markRoot(depthWalk.parseCommit(o));
+			} catch (IncorrectObjectTypeException notCommit) {
+				// Ignore non-commits in this loop.
+			}
+		}
+
+		RevCommit o;
+		while ((o = depthWalk.next()) != null) {
+			DepthWalk.Commit c = (DepthWalk.Commit) o;
+
+			// Commits at the boundary which aren't already shallow in
+			// the client need to be marked as such
+			if (c.getDepth() == depth && !clientShallowCommits.contains(c))
+				pckOut.writeString("shallow " + o.name());
+
+			// Commits not on the boundary which are shallow in the client
+			// need to become unshallowed
+			if (c.getDepth() < depth && clientShallowCommits.contains(c)) {
+				unshallowCommits.add(c.copy());
+				pckOut.writeString("unshallow " + c.name());
+			}
+		}
+
+		pckOut.end();
+	}
+
 	/**
 	 * Generate an advertisement of available refs and capabilities.
 	 *
@@ -488,6 +536,7 @@ public class UploadPack {
 		adv.advertiseCapability(OPTION_SIDE_BAND_64K);
 		adv.advertiseCapability(OPTION_THIN_PACK);
 		adv.advertiseCapability(OPTION_NO_PROGRESS);
+		adv.advertiseCapability(OPTION_SHALLOW);
 		if (!biDirectionalPipe)
 			adv.advertiseCapability(OPTION_NO_DONE);
 		adv.setDerefTags(true);
@@ -509,6 +558,17 @@ public class UploadPack {
 
 			if (line == PacketLineIn.END)
 				break;
+
+			if (line.startsWith("deepen ")) {
+				depth = Integer.parseInt(line.substring(7));
+				continue;
+			}
+
+			if (line.startsWith("shallow ")) {
+				clientShallowCommits.add(ObjectId.fromString(line.substring(8)));
+				continue;
+			}
+
 			if (!line.startsWith("want ") || line.length() < 45)
 				throw new PackProtocolException(MessageFormat.format(JGitText.get().expectedGot, "want", line));
 
@@ -536,6 +596,13 @@ public class UploadPack {
 			try {
 				line = pckIn.readString();
 			} catch (EOFException eof) {
+				// EOF on stateless RPC (aka smart HTTP) and non-shallow request
+				// means the client asked for the updated shallow/unshallow data,
+				// disconnected, and will try another request with actual want/have.
+				// Don't report the EOF here, its a bug in the protocol that the client
+				// just disconnects without sending an END.
+				if (!biDirectionalPipe && depth > 0)
+					return false;
 				throw eof;
 			}
 
@@ -887,6 +954,9 @@ public class UploadPack {
 				pw.setTagTargets(tagTargets);
 			}
 
+			if (depth > 0)
+				pw.setShallowPack(depth, unshallowCommits);
+
 			RevWalk rw = walk;
 			if (wantAll.isEmpty()) {
 				pw.preparePack(pm, wantIds, commonBase);