Bug 162655 [Undo] [IDE] - Undoing a delete should check for existence of resources to be restored
N20061027. - I deleted two projects (along with their content). I read the warning that undo delete cannot restore the content and said "OK." - Then I checked out those same projects from HEAD. - Then I selected "Undo Delete Resources." This overwrote my code with empty projects. I think that "Undo Delete Resources" should become invalid if the resources exist again, because you'll end up replacing content without keeping a backup.
bundles/org.eclipse.ui.ide/src/org/eclipse/ui/ide/undo/AbstractResourcesOperation.java
/**
	 * Compute the status for creating resources from the descriptions. A status
	 * severity of <code>OK</code> indicates that the create is likely to be
	 * successful. A status severity of <code>ERROR</code> indicates that the
	 * operation is no longer valid. Other status severities are open to
	 * interpretation by the caller.
	 * 
	 * Note this method may be called on initial creation of a resource, or when
	 * a create or delete operation is being undone or redone. Therefore, this
	 * method should check conditions that can change over the life of the
	 * operation, such as the existence of the information needed to carry out
	 * the operation. One-time static checks should typically be done by the
	 * caller (such as the action that creates the operation) so that the user
	 * is not continually prompted or warned about conditions that were
	 * acceptable at the time of original execution.
	 */
	protected IStatus computeCreateStatus() {
		if (resourceDescriptions == null || resourceDescriptions.length == 0) {
			markInvalid();
			return getErrorStatus(UndoMessages.AbstractResourcesOperation_NotEnoughInfo);
		}
		for (int i = 0; i < resourceDescriptions.length; i++) {
			if (!resourceDescriptions[i].isValid()) {
				markInvalid();
				return getErrorStatus(UndoMessages.AbstractResourcesOperation_InvalidRestoreInfo);
			}
		}
		return Status.OK_STATUS;
	}
	/**