Batch reference updates together for storage

clone, fetch and push can all update multiple references in a single
command invocation. Rather than performing sequential iteration
of each reference change inside of the application code, push this
down into the reference database where the implementation can take
advantage of the batch size and optimize itself.

For the local filesystem implementation the obvious optimization
is to write a packed-refs file when the repository is completely
empty. The initial clone, fetch or push into the destination may
have hundreds of new references. Writing all of these as loose
files is not efficient. This optimization is not implemented in
this commit and is left as an exercise for the reader to supply
in a future commit to JGit.

To make the API changes simple, define the BatchRefUpdate type and
implementation using the existing sequential behavior.

Change-Id: I8e1674f091e05e24e3ff56ccbc687a6d18a6a61e

2 files changed, 27 insertions, 8 deletions

diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/transport/BaseReceivePack.java b/org.eclipse.jgit/src/org/eclipse/jgit/transport/BaseReceivePack.java
index 9d72ef8680..e375221eeb 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/transport/BaseReceivePack.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/transport/BaseReceivePack.java
@@ -67,6 +67,7 @@ import java.util.concurrent.TimeUnit;
 import org.eclipse.jgit.errors.MissingObjectException;
 import org.eclipse.jgit.errors.PackProtocolException;
 import org.eclipse.jgit.internal.JGitText;
+import org.eclipse.jgit.lib.BatchRefUpdate;
 import org.eclipse.jgit.lib.Config;
 import org.eclipse.jgit.lib.Config.SectionParser;
 import org.eclipse.jgit.lib.Constants;
@@ -1139,12 +1140,20 @@ public abstract class BaseReceivePack {
 			pm.setDelayStart(250, TimeUnit.MILLISECONDS);
 			updating = pm;
 		}
-		updating.beginTask(JGitText.get().updatingReferences, toApply.size());
-		for (ReceiveCommand cmd : toApply) {
-			updating.update(1);
-			cmd.execute(this);
+
+		BatchRefUpdate batch = db.getRefDatabase().newBatchUpdate();
+		batch.setAllowNonFastForwards(isAllowNonFastForwards());
+		batch.setRefLogIdent(getRefLogIdent());
+		batch.setRefLogMessage("push", true);
+		batch.addCommand(toApply);
+		try {
+			batch.execute(walk, updating);
+		} catch (IOException err) {
+			for (ReceiveCommand cmd : toApply) {
+				if (cmd.getResult() == Result.NOT_ATTEMPTED)
+					cmd.reject(err);
+			}
 		}
-		updating.endTask();
 	}
 
 	/**
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/transport/ReceiveCommand.java b/org.eclipse.jgit/src/org/eclipse/jgit/transport/ReceiveCommand.java
index 26bbcdcbc8..4c7ffeccee 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/transport/ReceiveCommand.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/transport/ReceiveCommand.java
@@ -337,8 +337,7 @@ public class ReceiveCommand {
 				break;
 			}
 		} catch (IOException err) {
-			setResult(Result.REJECTED_OTHER_REASON, MessageFormat.format(
-					JGitText.get().lockError, err.getMessage()));
+			reject(err);
 		}
 	}
 
@@ -355,7 +354,13 @@ public class ReceiveCommand {
 		typeIsCorrect = true;
 	}
 
-	private void setResult(final RefUpdate.Result r) {
+	/**
+	 * Set the result of this command.
+	 *
+	 * @param r
+	 *            the new result code for this command.
+	 */
+	public void setResult(RefUpdate.Result r) {
 		switch (r) {
 		case NOT_ATTEMPTED:
 			setResult(Result.NOT_ATTEMPTED);
@@ -387,6 +392,11 @@ public class ReceiveCommand {
 		}
 	}
 
+	void reject(IOException err) {
+		setResult(Result.REJECTED_OTHER_REASON, MessageFormat.format(
+				JGitText.get().lockError, err.getMessage()));
+	}
+
 	@Override
 	public String toString() {
 		return getType().name() + ": " + getOldId().name() + " "