[development] Lineage module --- nested trees

[Earl Miles]

Earl Miles wrote:
>> The comment module uses a similar technique.  As discussed before,  
>> the better approach would be to add a generic nested tree algorithm  
>> to core.  Such algorithm could be re-used by the (i) comment module,  
>> (ii) book outlines, (iii) taxomomy trees, etc.  I wish merlinofchaos  
>> would turn this into a generic core API, rather than a contributed  
>> module.
> 
> Interestingly, I initially submitted this as a patch to core and was 
> immediately told it didn't belong there.
> 
> I can think about how to genericize the algorithm and make it available 
> to core somewhere. I'll have to look at the content module.

To elaborate a bit -- one of the reasons for core difficulty is that it simply 
doesn't work with multiple inheritance. My own answer to that, of course, is 
"Feh on multiple inheritance", and to just let it go. But it is an issue.

And I typed content when I meant comment.