Bug 123972 [Undo] Support approval of undoable operation execution
In GMF we do some common validation on our commands before we proceed to execute, undo or redo them. This validation is external to the command's ability to execute, undo or redo itself. Registering an IOperationApprover with the operation history for this of validation would give us an elegant solution. However, the IOperationApprover only supports approval of undo and redo. We also require support for approval of operation execution. Would you consider adding a proceedExecuting() method to the IOperationApprover interface, or to an extension of the IOperationApprover interface?
bundles/org.eclipse.core.commands/src/org/eclipse/core/commands/operations/DefaultOperationHistory.java
return Status.OK_STATUS;
	}
	/*
	 * (non-Javadoc)
	 * 
	 * @see org.eclipse.core.commands.operations.IOperationHistory#getRedoHistory(org.eclipse.core.commands.operations.IUndoContext)
	 */
	public IUndoableOperation[] getRedoHistory(IUndoContext context) {
		Assert.isNotNull(context);
		return filter(redoList, context);
	}
	/*
	 * (non-Javadoc)
	 * 
	 * @see org.eclipse.core.commands.operations.IOperationHistory#getOperation(org.eclipse.core.commands.operations.IUndoContext)
	 */
	public IUndoableOperation getRedoOperation(IUndoContext context) {
		Assert.isNotNull(context);
		synchronized (undoRedoHistoryLock) {
			for (int i = redoList.size() - 1; i >= 0; i--) {
				IUndoableOperation operation = (IUndoableOperation) redoList
						.get(i);
				if (operation.hasContext(context)) {
					return operation;
				}
			}
		}
		return null;
	}
	/*