Document that repo returned by SubmoduleAddCommand needs to be closed

Bug: 448570
Change-Id: I05be0a5b07f8e22f55637b9a3080362978368bcb
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

org.eclipse.jgit/src/org/eclipse/jgit/api/SubmoduleAddCommand.java

@@ -136,6 +136,17 @@ public class SubmoduleAddCommand extends
 		return SubmoduleWalk.forIndex(repo).setFilter(filter).next();
 	}
 
+	/**
+	 * Executes the {@code SubmoduleAddCommand}
+	 *
+	 * The {@code Repository} instance returned by this command needs to be
+	 * closed by the caller to free resources held by the {@code Repository}
+	 * instance. It is recommended to call this method as soon as you don't need
+	 * a reference to this {@code Repository} instance anymore.
+	 *
+	 * @return the newly created {@link Repository}
+	 * @throws GitAPIException
+	 */
 	public Repository call() throws GitAPIException {
 		checkCallable();
 		if (path == null || path.length() == 0)