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
IResource resource = resourceDescriptions[i].createResourceHandle();
			
			ruleArray[i * 3] = getWorkspaceRuleFactory().createRule(resource);
			
			ruleArray[i * 3 + 1] = getWorkspaceRuleFactory().modifyRule(
					resource);
			
			ruleArray[i * 3 + 2] = getWorkspaceRuleFactory().charsetRule(
					resource);
		}
		return MultiRule.combine(ruleArray);
	}
	/**
	 * Compute a scheduling rule for deleting resources.
	 * 
	 * @return a scheduling rule appropriate for deleting the resources
	 *         specified in the receiver.
	 */
	protected ISchedulingRule computeDeleteSchedulingRule() {
		ISchedulingRule[] ruleArray = new ISchedulingRule[resources.length*2];
		for (int i = 0; i < resources.length; i++) {
			ruleArray[i*2] = getWorkspaceRuleFactory().deleteRule(resources[i]);
			
			
			ruleArray[i*2+1] = getWorkspaceRuleFactory().modifyRule(resources[i]);
		}
		return MultiRule.combine(ruleArray);
	}
}