Program: 7835
Project: 7835
Buggy source:
public Object execute(final ExecutionEvent event) throws ExecutionException {
  final Repository repository=getRepository(true,event);
  if (repository == null)   return null;
  if (!canMerge(repository,event))   return null;
  MergeTargetSelectionDialog mergeTargetSelectionDialog=new MergeTargetSelectionDialog(getShell(event),repository);
  if (mergeTargetSelectionDialog.open() == IDialogConstants.OK_ID) {
    final String refName=mergeTargetSelectionDialog.getRefName();
    String jobname=NLS.bind(UIText.MergeAction_JobNameMerge,refName);
    final MergeOperation op=new MergeOperation(repository,refName);
    Job job=new Job(jobname){
      @Override protected IStatus run(      IProgressMonitor monitor){
        try {
          op.execute(monitor);
        }
 catch (        final CoreException e) {
          return e.getStatus();
        }
        return Status.OK_STATUS;
      }
    }
;
    job.setUser(true);
    job.addJobChangeListener(new JobChangeAdapter(){
      @Override public void done(      IJobChangeEvent cevent){
        IStatus result=cevent.getJob().getResult();
        if (result.getSeverity() == IStatus.CANCEL) {
          Display.getDefault().asyncExec(new Runnable(){
            public void run(){
              try {
                MessageDialog.openInformation(getShell(event),UIText.MergeAction_MergeCanceledTitle,UIText.MergeAction_MergeCanceledMessage);
              }
 catch (              ExecutionException e) {
                Activator.handleError(UIText.MergeAction_MergeCanceledMessage,null,true);
              }
            }
          }
);
        }
 else         if (!result.isOK()) {
          Activator.handleError(result.getMessage(),result.getException(),true);
        }
 else {
          Display.getDefault().asyncExec(new Runnable(){
            public void run(){
              try {
                MessageDialog.openInformation(getShell(event),UIText.MergeAction_MergeResultTitle,op.getResult().toString());
              }
 catch (              ExecutionException e) {
                Activator.handleError(op.getResult().toString(),null,true);
              }
            }
          }
);
        }
      }
    }
);
    job.schedule();
  }
  return null;
}

Fixed version (ground truth):
public Object execute(final ExecutionEvent event) throws ExecutionException {
  final Repository repository=getRepository(true,event);
  if (repository == null)   return null;
  if (!canMerge(repository,event))   return null;
  MergeTargetSelectionDialog mergeTargetSelectionDialog=new MergeTargetSelectionDialog(getShell(event),repository);
  if (mergeTargetSelectionDialog.open() == IDialogConstants.OK_ID) {
    final String refName=mergeTargetSelectionDialog.getRefName();
    String jobname=NLS.bind(UIText.MergeAction_JobNameMerge,refName);
    final MergeOperation op=new MergeOperation(repository,refName);
    Job job=new Job(jobname){
      @Override protected IStatus run(      IProgressMonitor monitor){
        try {
          op.execute(monitor);
        }
 catch (        final CoreException e) {
          return e.getStatus();
        }
        return Status.OK_STATUS;
      }
    }
;
    job.setUser(true);
    job.setRule(op.getSchedulingRule());
    job.addJobChangeListener(new JobChangeAdapter(){
      @Override public void done(      IJobChangeEvent cevent){
        IStatus result=cevent.getJob().getResult();
        if (result.getSeverity() == IStatus.CANCEL) {
          Display.getDefault().asyncExec(new Runnable(){
            public void run(){
              Shell shell=PlatformUI.getWorkbench().getActiveWorkbenchWindow().getShell();
              MessageDialog.openInformation(shell,UIText.MergeAction_MergeCanceledTitle,UIText.MergeAction_MergeCanceledMessage);
            }
          }
);
        }
 else         if (!result.isOK()) {
          Activator.handleError(result.getMessage(),result.getException(),true);
        }
 else {
          Display.getDefault().asyncExec(new Runnable(){
            public void run(){
              Shell shell=PlatformUI.getWorkbench().getActiveWorkbenchWindow().getShell();
              MessageDialog.openInformation(shell,UIText.MergeAction_MergeResultTitle,op.getResult().toString());
            }
          }
);
        }
      }
    }
);
    job.schedule();
  }
  return null;
}