Allow to perform PackedBatchRefUpdate without locking loose refs

Add another newBatchUpdate method in the RefDirectory where we can
control if the created PackedBatchRefUpdate will lock the loose refs or
not.

This can be useful in cases when we run programs which have exclusive
access to a Git repository and we know that locking loose refs is
unnecessary and just a performance loss.

Change-Id: I7d0932eb1598a3871a2281b1a049021380234df9

2 files changed, 24 insertions, 3 deletions

diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/PackedBatchRefUpdate.java b/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/PackedBatchRefUpdate.java
index 9c1d33dc3c..8b0ea4fcd6 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/PackedBatchRefUpdate.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/PackedBatchRefUpdate.java
@@ -86,10 +86,16 @@ import org.eclipse.jgit.util.RefList;
  */
 class PackedBatchRefUpdate extends BatchRefUpdate {
 	private RefDirectory refdb;
+	private boolean shouldLockLooseRefs;
 
 	PackedBatchRefUpdate(RefDirectory refdb) {
-		super(refdb);
-		this.refdb = refdb;
+		this(refdb, true);
+	}
+
+	PackedBatchRefUpdate(RefDirectory refdb, boolean shouldLockLooseRefs) {
+	  super(refdb);
+	  this.refdb = refdb;
+	  this.shouldLockLooseRefs = shouldLockLooseRefs;
 	}
 
 	/** {@inheritDoc} */
@@ -155,7 +161,7 @@ class PackedBatchRefUpdate extends BatchRefUpdate {
 		refdb.inProcessPackedRefsLock.lock();
 		try {
 			PackedRefList oldPackedList;
-			if (!refdb.isInClone()) {
+			if (!refdb.isInClone() && shouldLockLooseRefs) {
 				locks = lockLooseRefs(pending);
 				if (locks == null) {
 					return;
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/RefDirectory.java b/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/RefDirectory.java
index 07e38147f7..b46ffe3670 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/RefDirectory.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/RefDirectory.java
@@ -587,6 +587,21 @@ public class RefDirectory extends RefDatabase {
 		return new PackedBatchRefUpdate(this);
 	}
 
+	/**
+	 * Create a new batch update to attempt on this database.
+	 *
+	 * @param shouldLockLooseRefs
+	 *            whether loose refs should be locked during the batch ref
+	 *            update. Note that this should only be set to {@code false} if
+	 *            the application using this ensures that no other ref updates
+	 *            run concurrently to avoid lost updates caused by a race. In
+	 *            such cases it can improve performance.
+	 * @return a new batch update object
+	 */
+	public PackedBatchRefUpdate newBatchUpdate(boolean shouldLockLooseRefs) {
+		return new PackedBatchRefUpdate(this, shouldLockLooseRefs);
+	}
+
 	/** {@inheritDoc} */
 	@Override
 	public boolean performsAtomicTransactions() {