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/CopyResourcesOperation.java
AbstractCopyOrMoveResourcesOperation {
	IResource[] originalResources;
	ResourceDescription[] snapshotResourceDescriptions;
	/**
	 * Create a CopyResourcesOperation that copies a single resource to a new
	 * location. The new location includes the name of the copy.
	 * 
	 * @param resource
	 *            the resource to be copied
	 * @param newPath
	 *            the new workspace-relative path for the copy, including its
	 *            desired name.
	 * @param label
	 *            the label of the operation
	 */
	public CopyResourcesOperation(IResource resource, IPath newPath,
			String label) {
		super(new IResource[] { resource }, new IPath[] { newPath }, label);
		setOriginalResources(new IResource[] { resource });
	}
	/**
	 * Create a CopyResourcesOperation that copies all of the specified
	 * resources to a single target location. The original resource name will be
	 * used when copied to the new location.
	 * 
	 * @param resources