ref = null;
if (ref == null) {
RebaseTargetSelectionDialog rebaseTargetSelectionDialog = new RebaseTargetSelectionDialog(
getShell(event), repository);
if (rebaseTargetSelectionDialog.open() == IDialogConstants.OK_ID) {
String refName = rebaseTargetSelectionDialog.getRefName();
try {
ref = repository.getRef(refName);
} catch (IOException e) {
throw new ExecutionException(e.getMessage(), e);