BasePackFetchConnection: support negotiationTip feature

By default, Git will report, to the server, commits reachable from all local refs to find common commits in an attempt to reduce the size of the to-be-received packfile. If specified with negotiation tip, Git will only report commits reachable from the given tips. This is useful to speed up fetches when the user knows which local ref is likely to have commits in common with the upstream ref being fetched.

When negotation-tip is on, use the wanted refs instead of all refs as source of the "have" list to send.

This is controlled by the `fetch.usenegotationtip` flag, false by default. This works only for programmatic fetches and there is no support for it yet in the CLI.

Change-Id: I19f8fe48889bfe0ece7cdf78019b678ede5c6a32

1 files changed, 36 insertions, 2 deletions

diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/transport/BasePackFetchConnection.java b/org.eclipse.jgit/src/org/eclipse/jgit/transport/BasePackFetchConnection.java
index be36d2b834..8909380176 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/transport/BasePackFetchConnection.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/transport/BasePackFetchConnection.java
@@ -37,6 +37,7 @@ import java.util.HashSet;
 import java.util.LinkedHashSet;
 import java.util.List;
 import java.util.Set;
+import java.util.stream.Collectors;
 
 import org.eclipse.jgit.errors.PackProtocolException;
 import org.eclipse.jgit.errors.RemoteRepositoryException;
@@ -215,6 +216,8 @@ public abstract class BasePackFetchConnection extends BasePackConnection
 
 	private boolean allowOfsDelta;
 
+	private boolean useNegotiationTip;
+
 	private boolean noDone;
 
 	private boolean noProgress;
@@ -259,9 +262,11 @@ public abstract class BasePackFetchConnection extends BasePackConnection
 			final FetchConfig cfg = getFetchConfig();
 			allowOfsDelta = cfg.allowOfsDelta;
 			maxHaves = cfg.maxHaves;
+			useNegotiationTip = cfg.useNegotiationTip;
 		} else {
 			allowOfsDelta = true;
 			maxHaves = Integer.MAX_VALUE;
+			useNegotiationTip = false;
 		}
 
 		includeTags = transport.getTagOpt() != TagOpt.NO_TAGS;
@@ -297,14 +302,35 @@ public abstract class BasePackFetchConnection extends BasePackConnection
 
 		final int maxHaves;
 
+		final boolean useNegotiationTip;
+
 		FetchConfig(Config c) {
 			allowOfsDelta = c.getBoolean("repack", "usedeltabaseoffset", true); //$NON-NLS-1$ //$NON-NLS-2$
 			maxHaves = c.getInt("fetch", "maxhaves", Integer.MAX_VALUE); //$NON-NLS-1$ //$NON-NLS-2$
+			useNegotiationTip = c.getBoolean("fetch", "usenegotiationtip", //$NON-NLS-1$ //$NON-NLS-2$
+					false);
 		}
 
 		FetchConfig(boolean allowOfsDelta, int maxHaves) {
+			this(allowOfsDelta, maxHaves, false);
+		}
+
+		/**
+		 * @param allowOfsDelta
+		 *            when true optimizes the pack size by deltafying base
+		 *            object
+		 * @param maxHaves
+		 *            max haves to be sent per negotiation
+		 * @param useNegotiationTip
+		 *            if true uses the wanted refs instead of all refs as source
+		 *            of the "have" list to send.
+		 * @since 6.6
+		 */
+		FetchConfig(boolean allowOfsDelta, int maxHaves,
+				boolean useNegotiationTip) {
 			this.allowOfsDelta = allowOfsDelta;
 			this.maxHaves = maxHaves;
+			this.useNegotiationTip = useNegotiationTip;
 		}
 	}
 
@@ -384,7 +410,7 @@ public abstract class BasePackFetchConnection extends BasePackConnection
 			noProgress = monitor == NullProgressMonitor.INSTANCE;
 
 			markRefsAdvertised();
-			markReachable(have, maxTimeWanted(want));
+			markReachable(want, have, maxTimeWanted(want));
 
 			if (TransferConfig.ProtocolVersion.V2
 					.equals(getProtocolVersion())) {
@@ -662,9 +688,17 @@ public abstract class BasePackFetchConnection extends BasePackConnection
 		return maxTime;
 	}
 
-	private void markReachable(Set<ObjectId> have, int maxTime)
+	private void markReachable(Collection<Ref> want, Set<ObjectId> have,
+			int maxTime)
 			throws IOException {
+		Set<String> wantRefs = want.stream().map(Ref::getName)
+				.collect(Collectors.toSet());
+
 		for (Ref r : local.getRefDatabase().getRefs()) {
+			if (useNegotiationTip && !wantRefs.contains(r.getName())) {
+				continue;
+			}
+
 			ObjectId id = r.getPeeledObjectId();
 			if (id == null)
 				id = r.getObjectId();