Bug 161738 [Undo] - API - promote ability to quietly compute status to operations API
bundles/org.eclipse.ui.ide/src/org/eclipse/ui/internal/ide/undo/WorkspaceUndoMonitor.java
}
		IUndoableOperation currentOp = getOperationHistory().getUndoOperation(
				WorkspaceUndoUtil.getWorkspaceUndoContext());
		
		if (currentOp == null) {
			resetChangeCount();
			return;
		}
		
		if (!currentOp.canUndo()) {
			flushWorkspaceHistory(currentOp);
			return;
		}
		
		
		
		
		if (currentOp instanceof AbstractWorkspaceOperation) {
			AbstractWorkspaceOperation op = (AbstractWorkspaceOperation) currentOp;
			op.setQuietCompute(true);
			IStatus status = op.computeUndoableStatus(null);
			op.setQuietCompute(false);
			if (status.getSeverity() == IStatus.ERROR) {
				flushWorkspaceHistory(currentOp);
			}
		}
		resetChangeCount();
	}
	/**
	 * Flush the undo and redo history for the workspace undo context.