Re: [PATCH 2/5] add object-cache infrastructure

[Illia Bobyr <Illia.Bobyr@ronin-capital.com>]

On 7/14/2011 3:04 AM, Clemens Buchacher wrote:
> On Tue, Jul 12, 2011 at 05:36:07PM -0400, Jeff King wrote:
>> In the normal case of applying patch B on top of patch A, it doesn't
>> matter if we use per-hunk patch-ids or normal patch-ids. Because even if
>> we decide to actually go through with the merge of B on top of A, any
>> hunks that _would have_ had their per-hunk patch-ids match will merge
>> cleanly.
>>
>> But in the real world, it is about applying patch Z on top of patches
>> A..Y, where Z has similar hunks to patch N. And then it _does_ make a
>> difference, because it is about skipping hunks from Z that are already
>> in N, but will end up applied on top of Y. And what's in Y and what's in
>> N may be quite different.
>>
>> Does that sound right?
> Yes, exactly.
>
> And one possible solution would be to drop all hunks from Z which
> are already somewhere in A..Y. But that undermines the whole
> changeset idea.
>
> If we detect the similarities between Z and N, then we could rebase
> Z to N, make the user resolve any conflicts, which should make more
> sense than what we would have between Z and Y. Then we have Z' on
> top of N:
>
>    Z      Z'     Z"
>   /      /      /
> A--..--N--..--Y
>
> Subsequently we rebase Z' to Y, at which point only changes remain
> that we disagreed with. For those we may have to do conflict
> resolution again. So, in some cases this approach could result in
> more work.

This is where rerere helps, AFAIU.
And if the conflict is non-trivial there is a chance that it is really 
something you would like to take a look at.