Teach UploadPack to support filtering by blob size

Teach UploadPack to advertise the filter capability and support a
"filter" line in the request, accepting blob sizes only, if the
configuration variable "uploadpack.allowfilter" is true. This feature is
currently in the "master" branch of Git, and as of the time of writing,
this feature is to be released in Git 2.17.

This is incomplete in that the filter-by-sparse-specification feature
also supported by Git is not included in this patch.

If a JGit server were to be patched with this commit, and a repository
on that server configured with RequestPolicy.ANY or
RequestPolicy.REACHABLE_COMMIT_TIP, a Git client built from the "master"
branch would be able to perform a partial clone.

Change-Id: If72b4b422c06ab432137e9e5272d353b14b73259
Signed-off-by: Jonathan Tan <jonathantanmy@google.com>

org.eclipse.jgit.test/tst/org/eclipse/jgit/transport/UploadPackTest.java

@@ -13,6 +13,7 @@ import org.eclipse.jgit.lib.NullProgressMonitor;
 import org.eclipse.jgit.lib.Repository;
 import org.eclipse.jgit.revwalk.RevBlob;
 import org.eclipse.jgit.revwalk.RevCommit;
+import org.eclipse.jgit.revwalk.RevTree;
 import org.eclipse.jgit.transport.UploadPack.RequestPolicy;
 import org.eclipse.jgit.transport.resolver.ServiceNotAuthorizedException;
 import org.eclipse.jgit.transport.resolver.ServiceNotEnabledException;
@@ -170,4 +171,149 @@ public class UploadPackTest {
 					Collections.singletonList(new RefSpec(blob.name())));
 		}
 	}
+
+	@Test
+	public void testFetchWithBlobNoneFilter() throws Exception {
+		InMemoryRepository server2 = newRepo("server2");
+		TestRepository<InMemoryRepository> remote =
+				new TestRepository<>(server2);
+		RevBlob blob1 = remote.blob("foobar");
+		RevBlob blob2 = remote.blob("fooba");
+		RevTree tree = remote.tree(
+				remote.file("1", blob1), remote.file("2", blob2));
+		RevCommit commit = remote.commit(tree);
+		remote.update("master", commit);
+
+		server2.getConfig().setBoolean("uploadpack", null, "allowfilter", true);
+
+		testProtocol = new TestProtocol<>(
+				new UploadPackFactory<Object>() {
+					@Override
+					public UploadPack create(Object req, Repository db)
+							throws ServiceNotEnabledException,
+							ServiceNotAuthorizedException {
+						UploadPack up = new UploadPack(db);
+						return up;
+					}
+				}, null);
+		uri = testProtocol.register(ctx, server2);
+
+		try (Transport tn = testProtocol.open(uri, client, "server2")) {
+			tn.setFilterBlobLimit(0);
+			tn.fetch(NullProgressMonitor.INSTANCE,
+					Collections.singletonList(new RefSpec(commit.name())));
+			assertTrue(client.hasObject(tree.toObjectId()));
+			assertFalse(client.hasObject(blob1.toObjectId()));
+			assertFalse(client.hasObject(blob2.toObjectId()));
+		}
+	}
+
+	@Test
+	public void testFetchWithBlobLimitFilter() throws Exception {
+		InMemoryRepository server2 = newRepo("server2");
+		TestRepository<InMemoryRepository> remote =
+				new TestRepository<>(server2);
+		RevBlob longBlob = remote.blob("foobar");
+		RevBlob shortBlob = remote.blob("fooba");
+		RevTree tree = remote.tree(
+				remote.file("1", longBlob), remote.file("2", shortBlob));
+		RevCommit commit = remote.commit(tree);
+		remote.update("master", commit);
+
+		server2.getConfig().setBoolean("uploadpack", null, "allowfilter", true);
+
+		testProtocol = new TestProtocol<>(
+				new UploadPackFactory<Object>() {
+					@Override
+					public UploadPack create(Object req, Repository db)
+							throws ServiceNotEnabledException,
+							ServiceNotAuthorizedException {
+						UploadPack up = new UploadPack(db);
+						return up;
+					}
+				}, null);
+		uri = testProtocol.register(ctx, server2);
+
+		try (Transport tn = testProtocol.open(uri, client, "server2")) {
+			tn.setFilterBlobLimit(5);
+			tn.fetch(NullProgressMonitor.INSTANCE,
+					Collections.singletonList(new RefSpec(commit.name())));
+			assertFalse(client.hasObject(longBlob.toObjectId()));
+			assertTrue(client.hasObject(shortBlob.toObjectId()));
+		}
+	}
+
+	@Test
+	public void testFetchWithBlobLimitFilterAndBitmaps() throws Exception {
+		InMemoryRepository server2 = newRepo("server2");
+		TestRepository<InMemoryRepository> remote =
+				new TestRepository<>(server2);
+		RevBlob longBlob = remote.blob("foobar");
+		RevBlob shortBlob = remote.blob("fooba");
+		RevTree tree = remote.tree(
+				remote.file("1", longBlob), remote.file("2", shortBlob));
+		RevCommit commit = remote.commit(tree);
+		remote.update("master", commit);
+
+		server2.getConfig().setBoolean("uploadpack", null, "allowfilter", true);
+
+		// generate bitmaps
+		new DfsGarbageCollector(server2).pack(null);
+		server2.scanForRepoChanges();
+
+		testProtocol = new TestProtocol<>(
+				new UploadPackFactory<Object>() {
+					@Override
+					public UploadPack create(Object req, Repository db)
+							throws ServiceNotEnabledException,
+							ServiceNotAuthorizedException {
+						UploadPack up = new UploadPack(db);
+						return up;
+					}
+				}, null);
+		uri = testProtocol.register(ctx, server2);
+
+		try (Transport tn = testProtocol.open(uri, client, "server2")) {
+			tn.setFilterBlobLimit(5);
+			tn.fetch(NullProgressMonitor.INSTANCE,
+					Collections.singletonList(new RefSpec(commit.name())));
+			assertFalse(client.hasObject(longBlob.toObjectId()));
+			assertTrue(client.hasObject(shortBlob.toObjectId()));
+		}
+	}
+
+	@Test
+	public void testFetchWithNonSupportingServer() throws Exception {
+		InMemoryRepository server2 = newRepo("server2");
+		TestRepository<InMemoryRepository> remote =
+				new TestRepository<>(server2);
+		RevBlob blob = remote.blob("foo");
+		RevTree tree = remote.tree(remote.file("1", blob));
+		RevCommit commit = remote.commit(tree);
+		remote.update("master", commit);
+
+		server2.getConfig().setBoolean("uploadpack", null, "allowfilter", false);
+
+		testProtocol = new TestProtocol<>(
+				new UploadPackFactory<Object>() {
+					@Override
+					public UploadPack create(Object req, Repository db)
+							throws ServiceNotEnabledException,
+							ServiceNotAuthorizedException {
+						UploadPack up = new UploadPack(db);
+						return up;
+					}
+				}, null);
+		uri = testProtocol.register(ctx, server2);
+
+		try (Transport tn = testProtocol.open(uri, client, "server2")) {
+			tn.setFilterBlobLimit(0);
+
+			thrown.expect(TransportException.class);
+			thrown.expectMessage("filter requires server to advertise that capability");
+
+			tn.fetch(NullProgressMonitor.INSTANCE,
+					Collections.singletonList(new RefSpec(commit.name())));
+		}
+	}
 }

org.eclipse.jgit/resources/org/eclipse/jgit/internal/JGitText.properties

@@ -307,6 +307,7 @@ fileIsTooLarge=File is too large: {0}
 fileModeNotSetForPath=FileMode not set for path {0}
 filterExecutionFailed=Execution of filter command ''{0}'' on file ''{1}'' failed
 filterExecutionFailedRc=Execution of filter command ''{0}'' on file ''{1}'' failed with return code ''{2}'', message on stderr: ''{3}''
+filterRequiresCapability=filter requires server to advertise that capability
 findingGarbage=Finding garbage
 flagIsDisposed={0} is disposed.
 flagNotFromThis={0} not from this.
@@ -358,6 +359,7 @@ invalidCommitParentNumber=Invalid commit parent number
 invalidDepth=Invalid depth: {0}
 invalidEncryption=Invalid encryption
 invalidExpandWildcard=ExpandFromSource on a refspec that can have mismatched wildcards does not make sense.
+invalidFilter=Invalid filter: {0}
 invalidGitdirRef = Invalid .git reference in file ''{0}''
 invalidGitType=invalid git type: {0}
 invalidId=Invalid id: {0}
@@ -664,6 +666,7 @@ threadInterruptedWhileRunning="Current thread interrupted while running {0}"
 timeIsUncertain=Time is uncertain
 timerAlreadyTerminated=Timer already terminated
 tooManyCommands=Too many commands
+tooManyFilters=Too many "filter" lines in request
 tooManyIncludeRecursions=Too many recursions; circular includes in config file(s)?
 topologicalSortRequired=Topological sort required.
 transactionAborted=transaction aborted

org.eclipse.jgit/src/org/eclipse/jgit/internal/JGitText.java

@@ -368,6 +368,7 @@ public class JGitText extends TranslationBundle {
 	/***/ public String fileModeNotSetForPath;
 	/***/ public String filterExecutionFailed;
 	/***/ public String filterExecutionFailedRc;
+	/***/ public String filterRequiresCapability;
 	/***/ public String findingGarbage;
 	/***/ public String flagIsDisposed;
 	/***/ public String flagNotFromThis;
@@ -419,6 +420,7 @@ public class JGitText extends TranslationBundle {
 	/***/ public String invalidDepth;
 	/***/ public String invalidEncryption;
 	/***/ public String invalidExpandWildcard;
+	/***/ public String invalidFilter;
 	/***/ public String invalidGitdirRef;
 	/***/ public String invalidGitType;
 	/***/ public String invalidId;
@@ -726,6 +728,7 @@ public class JGitText extends TranslationBundle {
 	/***/ public String timeIsUncertain;
 	/***/ public String timerAlreadyTerminated;
 	/***/ public String tooManyCommands;
+	/***/ public String tooManyFilters;
 	/***/ public String tooManyIncludeRecursions;
 	/***/ public String topologicalSortRequired;
 	/***/ public String transportExceptionBadRef;

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

@@ -303,6 +303,8 @@ public class PackWriter implements AutoCloseable {
 
 	private ObjectCountCallback callback;
 
+	private long filterBlobLimit = -1;
+
 	/**
 	 * Create writer for specified repository.
 	 * <p>
@@ -638,6 +640,14 @@ public class PackWriter implements AutoCloseable {
 		this.unshallowObjects = unshallow;
 	}
 
+	/**
+	 * @param bytes exclude blobs of size greater than this
+	 * @since 5.0
+	 */
+	public void setFilterBlobLimit(long bytes) {
+		filterBlobLimit = bytes;
+	}
+
 	/**
 	 * Returns objects number in a pack file that was created by this writer.
 	 *
@@ -1960,7 +1970,7 @@ public class PackWriter implements AutoCloseable {
 				byte[] pathBuf = walker.getPathBuffer();
 				int pathLen = walker.getPathLength();
 				bases.addBase(o.getType(), pathBuf, pathLen, pathHash);
-				addObject(o, pathHash);
+				filterAndAddObject(o, o.getType(), pathHash);
 				countingMonitor.update(1);
 			}
 		} else {
@@ -1970,7 +1980,7 @@ public class PackWriter implements AutoCloseable {
 					continue;
 				if (exclude(o))
 					continue;
-				addObject(o, walker.getPathHashCode());
+				filterAndAddObject(o, o.getType(), walker.getPathHashCode());
 				countingMonitor.update(1);
 			}
 		}
@@ -2003,7 +2013,7 @@ public class PackWriter implements AutoCloseable {
 				needBitmap.remove(objectId);
 				continue;
 			}
-			addObject(objectId, obj.getType(), 0);
+			filterAndAddObject(objectId, obj.getType(), 0);
 		}
 
 		if (thin)
@@ -2062,6 +2072,24 @@ public class PackWriter implements AutoCloseable {
 		objectsMap.add(otp);
 	}
 
+	/**
+	 * Adds the given object as an object to be packed, first performing
+	 * filtering on blobs at or exceeding a given size.
+	 *
+	 * @see #setFilterBlobLimit
+	 */
+	private void filterAndAddObject(@NonNull AnyObjectId src, int type,
+			int pathHashCode) throws IOException {
+		// Check if this object needs to be rejected, doing the cheaper
+		// checks first.
+		boolean reject = filterBlobLimit >= 0 &&
+			type == OBJ_BLOB &&
+			reader.getObjectSize(src, OBJ_BLOB) > filterBlobLimit;
+		if (!reject) {
+			addObject(src, type, pathHashCode);
+		}
+	}
+
 	private boolean exclude(AnyObjectId objectId) {
 		if (excludeInPacks == null)
 			return false;

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

@@ -200,6 +200,13 @@ public abstract class BasePackFetchConnection extends BasePackConnection
 	 */
 	public static final String OPTION_ALLOW_REACHABLE_SHA1_IN_WANT = GitProtocolConstants.OPTION_ALLOW_REACHABLE_SHA1_IN_WANT;
 
+	/**
+	 * The client specified a filter expression.
+	 *
+	 * @since 5.0
+	 */
+	public static final String OPTION_FILTER = GitProtocolConstants.OPTION_FILTER;
+
 	private final RevWalk walk;
 
 	/** All commits that are immediately reachable by a local ref. */
@@ -242,6 +249,9 @@ public abstract class BasePackFetchConnection extends BasePackConnection
 
 	private PacketLineOut pckState;
 
+	/** If not -1, the maximum blob size to be sent to the server. */
+	private final long filterBlobLimit;
+
 	/**
 	 * Create a new connection to fetch using the native git transport.
 	 *
@@ -262,6 +272,7 @@ public abstract class BasePackFetchConnection extends BasePackConnection
 		}
 		includeTags = transport.getTagOpt() != TagOpt.NO_TAGS;
 		thinPack = transport.isFetchThin();
+		filterBlobLimit = transport.getFilterBlobLimit();
 
 		if (local != null) {
 			walk = new RevWalk(local);
@@ -524,6 +535,11 @@ public abstract class BasePackFetchConnection extends BasePackConnection
 		if (first) {
 			return false;
 		}
+		if (filterBlobLimit == 0) {
+			p.writeString(OPTION_FILTER + " blob:none");
+		} else if (filterBlobLimit > 0) {
+			p.writeString(OPTION_FILTER + " blob:limit=" + filterBlobLimit);
+		}
 		p.end();
 		outNeedsEnd = false;
 		return true;
@@ -564,6 +580,11 @@ public abstract class BasePackFetchConnection extends BasePackConnection
 					OPTION_MULTI_ACK_DETAILED));
 		}
 
+		if (filterBlobLimit >= 0 && !wantCapability(line, OPTION_FILTER)) {
+			throw new PackProtocolException(uri,
+					JGitText.get().filterRequiresCapability);
+		}
+
 		addUserAgentCapability(line);
 		return line.toString();
 	}

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

@@ -151,6 +151,13 @@ public class GitProtocolConstants {
 	 */
 	public static final String OPTION_PUSH_CERT = "push-cert"; //$NON-NLS-1$
 
+	/**
+	 * The client specified a filter expression.
+	 *
+	 * @since 5.0
+	 */
+	public static final String OPTION_FILTER = "filter"; //$NON-NLS-1$
+
 	/**
 	 * The client supports atomic pushes. If this option is used, the server
 	 * will update all refs within one atomic transaction.

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

@@ -101,6 +101,7 @@ public class TransferConfig {
 	private final boolean safeForMacOS;
 	private final boolean allowTipSha1InWant;
 	private final boolean allowReachableSha1InWant;
+	private final boolean allowFilter;
 	final String[] hideRefs;
 
 	TransferConfig(final Repository db) {
@@ -153,6 +154,8 @@ public class TransferConfig {
 				"uploadpack", "allowtipsha1inwant", false); //$NON-NLS-1$ //$NON-NLS-2$
 		allowReachableSha1InWant = rc.getBoolean(
 				"uploadpack", "allowreachablesha1inwant", false); //$NON-NLS-1$ //$NON-NLS-2$
+		allowFilter = rc.getBoolean(
+				"uploadpack", "allowfilter", false); //$NON-NLS-1$ //$NON-NLS-2$
 		hideRefs = rc.getStringList("uploadpack", null, "hiderefs"); //$NON-NLS-1$ //$NON-NLS-2$
 	}
 
@@ -219,6 +222,14 @@ public class TransferConfig {
 		return allowReachableSha1InWant;
 	}
 
+	/**
+	 * @return true if clients are allowed to specify a "filter" line
+	 * @since 5.0
+	 */
+	public boolean isAllowFilter() {
+		return allowFilter;
+	}
+
 	/**
 	 * Get {@link org.eclipse.jgit.transport.RefFilter} respecting configured
 	 * hidden refs.

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

@@ -791,6 +791,8 @@ public abstract class Transport implements AutoCloseable {
 	/** Should refs no longer on the source be pruned from the destination? */
 	private boolean removeDeletedRefs;
 
+	private long filterBlobLimit = -1;
+
 	/** Timeout in seconds to wait before aborting an IO read or write. */
 	private int timeout;
 
@@ -1065,6 +1067,23 @@ public abstract class Transport implements AutoCloseable {
 		removeDeletedRefs = remove;
 	}
 
+	/**
+	 * @return the last value passed to {@link #setFilterBlobLimit}, or -1 if
+	 *         it was never invoked.
+	 * @since 5.0
+	 */
+	public long getFilterBlobLimit() {
+		return filterBlobLimit;
+	}
+
+	/**
+	 * @param bytes exclude blobs of size greater than this
+	 * @since 5.0
+	 */
+	public void setFilterBlobLimit(final long bytes) {
+		filterBlobLimit = bytes;
+	}
+
 	/**
 	 * Apply provided remote configuration on this transport.
 	 *

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

@@ -47,6 +47,7 @@ import static org.eclipse.jgit.lib.RefDatabase.ALL;
 import static org.eclipse.jgit.transport.GitProtocolConstants.OPTION_AGENT;
 import static org.eclipse.jgit.transport.GitProtocolConstants.OPTION_ALLOW_REACHABLE_SHA1_IN_WANT;
 import static org.eclipse.jgit.transport.GitProtocolConstants.OPTION_ALLOW_TIP_SHA1_IN_WANT;
+import static org.eclipse.jgit.transport.GitProtocolConstants.OPTION_FILTER;
 import static org.eclipse.jgit.transport.GitProtocolConstants.OPTION_INCLUDE_TAG;
 import static org.eclipse.jgit.transport.GitProtocolConstants.OPTION_MULTI_ACK;
 import static org.eclipse.jgit.transport.GitProtocolConstants.OPTION_MULTI_ACK_DETAILED;
@@ -317,6 +318,8 @@ public class UploadPack {
 
 	private PackStatistics statistics;
 
+	private long filterBlobLimit = -1;
+
 	/**
 	 * Create a new pack upload for an open repository.
 	 *
@@ -942,6 +945,9 @@ public class UploadPack {
 				|| policy == null)
 			adv.advertiseCapability(OPTION_ALLOW_REACHABLE_SHA1_IN_WANT);
 		adv.advertiseCapability(OPTION_AGENT, UserAgent.get());
+		if (transferConfig.isAllowFilter()) {
+			adv.advertiseCapability(OPTION_FILTER);
+		}
 		adv.setDerefTags(true);
 		Map<String, Ref> advertisedOrDefaultRefs = getAdvertisedOrDefaultRefs();
 		findSymrefs(adv, advertisedOrDefaultRefs);
@@ -982,6 +988,7 @@ public class UploadPack {
 
 	private void recvWants() throws IOException {
 		boolean isFirst = true;
+		boolean filterReceived = false;
 		for (;;) {
 			String line;
 			try {
@@ -1010,6 +1017,41 @@ public class UploadPack {
 				continue;
 			}
 
+			if (transferConfig.isAllowFilter()
+					&& line.startsWith(OPTION_FILTER + " ")) { //$NON-NLS-1$
+				String arg = line.substring(OPTION_FILTER.length() + 1);
+
+				if (filterReceived) {
+					throw new PackProtocolException(JGitText.get().tooManyFilters);
+				}
+				filterReceived = true;
+
+				if (arg.equals("blob:none")) {
+					filterBlobLimit = 0;
+				} else if (arg.startsWith("blob:limit=")) {
+					try {
+						filterBlobLimit = Long.parseLong(arg.substring("blob:limit=".length()));
+					} catch (NumberFormatException e) {
+						throw new PackProtocolException(
+								MessageFormat.format(JGitText.get().invalidFilter,
+										arg));
+					}
+				}
+				/*
+				 * We must have (1) either "blob:none" or
+				 * "blob:limit=" set (because we only support
+				 * blob size limits for now), and (2) if the
+				 * latter, then it must be nonnegative. Throw
+				 * if (1) or (2) is not met.
+				 */
+				if (filterBlobLimit < 0) {
+					throw new PackProtocolException(
+							MessageFormat.format(JGitText.get().invalidFilter,
+									arg));
+				}
+				continue;
+			}
+
 			if (!line.startsWith("want ") || line.length() < 45) //$NON-NLS-1$
 				throw new PackProtocolException(MessageFormat.format(JGitText.get().expectedGot, "want", line)); //$NON-NLS-1$
 
@@ -1547,7 +1589,12 @@ public class UploadPack {
 				accumulator);
 		try {
 			pw.setIndexDisabled(true);
-			pw.setUseCachedPacks(true);
+			if (filterBlobLimit >= 0) {
+				pw.setFilterBlobLimit(filterBlobLimit);
+				pw.setUseCachedPacks(false);
+			} else {
+				pw.setUseCachedPacks(true);
+			}
 			pw.setUseBitmaps(depth == 0 && clientShallowCommits.isEmpty());
 			pw.setClientShallowCommits(clientShallowCommits);
 			pw.setReuseDeltaCommits(true);