Re: Add "--show-all" revision walker flag for debugging

[Junio C Hamano <gitster@pobox.com>]

Junio C Hamano <gitster@pobox.com> writes:

> Linus Torvalds <torvalds@linux-foundation.org> writes:
>
>> The real issue is that it doesn't work. I thought about it, and with 
>> multiple roots (which _can_ get merged together) it just isn't something 
>> that actually helps.
>>
>> If you couldn't merge across roots, you could have a "uuid+generation 
>> header", but the moment you have multiple roots it actually gets quite 
>> complex.
>>
>> So scratch the generation header.  It's not the answer.
>
> I do not think multiple roots can be helped without going all
> the way down to the roots, and I think it can be proven.

Ah, please scratch that comment.  I was puzzled but did not
understand what you meant by uuid+generation.

You are right.  If we cannot tell if we are dealing with
disconnected history, we would always need to play safe and do
the clean-up like what I suggested earlier using merge-base
traversal, which could be costly, and we do not want to pay that
penalty in a connected history, which should be the normal case.

Generation header does not help us detect that case, so it is
not useful.