[PATCH] revset: allow negative integers to list child revs

[Sean Farley]

Pierre-Yves David writes:

> On 10/07/2014 11:40 AM, Sean Farley wrote:
>>
>> Pierre-Yves David writes:
>>
>>> On 10/04/2014 09:57 AM, Sean Farley wrote:
>>>> # HG changeset patch
>>>> # User Sean Farley <sean.michael.farley at gmail.com>
>>>> # Date 1412441841 25200
>>>> #      Sat Oct 04 09:57:21 2014 -0700
>>>> # Node ID c3bd6d6457bf42d2fbcaba89cf0418a0d0604239
>>>> # Parent  78c916f24dd99a56e4c29153a5df3bd7d1c40edd
>>>> revset: allow negative integers to list child revs
>>>
>>> Quick reply on various subject.
>>>
>>> As X^1 and X^2 return a single revision (per X) (short version for p1(X)
>>> and P2(X)) It would be a bad idea to have X^-1 return multiple revision.
>>
>> I agree.
>>
>>> first(children(X)) have less good defined semantic as first(parents(X))
>>> as it no deterministic and will change over time. the first parent of a
>>> changeset is carved in stone. The amount of Children change over time
>>> and with history rewriting, their order change over time. So you cannot
>>> really predict the order. You need to (a) have one parent or (b) look
>>> the number up (c) use a more precise revsets:
>>>     children(X) and ::bookmarkname
>>>     children(X) and desc(yyy)
>>
>> They should always be returned in the revlog order. That is what we
>> currently do with referring to children via revision numbers. This would
>> be no added confusion.
>
> You got me wrong. Their will of course be returned in revlog order. This 
> means that if you have three child A, B, C. You initially have
>
>    children(X) = A, B, C
>
> Then you amend A. So you get
>
>    children(X) = B, C, A
>
> And C get touched. So you get
>
>
>    children(X) = B, A, C
>
> Then you pull a new version X from someone with a children D. You evolve 
> and you end up with:
>
>    children(X) = D, B, A, C
>
> So you cannot blindly rely on c(X, 1) to give you stable result. And 
> normal human being have too look up the revset or use more precise revset.
>
> (will get to reply to the rest later)

Yes, of course, but this is derailing the current discussion. We have
the concept of local revision numbers and this patch is a way to refer
to that. I would suggest another discussion about the order of
children().