reftable: clarify comment

Change-Id: I16e32aeb325b604eb31f84db18a214f792395941
Signed-off-by: Han-Wen Nienhuys <hanwen@google.com>
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/FileReftableStack.java

@@ -396,7 +396,7 @@ public class FileReftableStack implements AutoCloseable {
 	 *
 	 * @param w
 	 *            writer to write data to a reftable under construction
-	 * @return true if the transaction.
+	 * @return true if the transaction was successful.
 	 * @throws IOException
 	 *             on I/O problems
 	 */