Make sure the "Object too large..." error is printed to the client

When receiving and object larger than receive.maxObjectSizeLimit, Gerrit
relied on the JGits ReceivePack.receive to print out the error message.
However, JGit didn't print out this error always. Sometimes it would
print the error and throw UnpackException and sometimes it would only
throw the UnpackException leaving the user without proper explanation
why the object was rejected.

With this change we print the error from Gerrit.

Change-Id: I5165ce0be86c91abf0ad02b5f7d8d2b1000dc493

gerrit-sshd/src/main/java/com/google/gerrit/sshd/commands/Receive.java

@@ -24,6 +24,7 @@ import com.google.gerrit.server.git.VisibleRefFilter;
 import com.google.gerrit.sshd.AbstractGitCommand;
 import com.google.inject.Inject;
 
+import org.eclipse.jgit.errors.TooLargeObjectInPackException;
 import org.eclipse.jgit.errors.UnpackException;
 import org.eclipse.jgit.lib.Ref;
 import org.eclipse.jgit.transport.AdvertiseRefsHook;
@@ -31,6 +32,7 @@ import org.eclipse.jgit.transport.ReceivePack;
 import org.kohsuke.args4j.Option;
 
 import java.io.IOException;
+import java.io.PrintWriter;
 import java.util.ArrayList;
 import java.util.HashSet;
 import java.util.List;
@@ -92,6 +94,15 @@ final class Receive extends AbstractGitCommand {
       receive.advertiseHistory();
       rp.receive(in, out, err);
     } catch (UnpackException badStream) {
+      // In case this was caused by the user pushing an object whose size
+      // is larger than the receive.maxObjectSizeLimit gerrit.config parameter
+      // we want to present this error to the user
+      if (badStream.getCause() instanceof TooLargeObjectInPackException) {
+        PrintWriter p = toPrintWriter(err);
+        p.print("error: " + badStream.getCause().getMessage() + "\n");
+        p.flush();
+      }
+
       // This may have been triggered by branch level access controls.
       // Log what the heck is going on, as detailed as we can.
       //