Re: [PATCH 2/3] path-walk: fix setup of pending objects

> On Wed, Aug 20, 2025 at 06:39:55PM +0000, Derrick Stolee via GitGitGadget wrote:
>> From: Derrick Stolee <stolee@gmail.com>
>>
>> The previous change established a buggy instance of 'git repack -adf
>> --path-walk' when there exist paths that are tracked in the index and
>> that is the only instance of those paths in the history of the
>> repository. This change fixes that bug.
>>
>> The core problem here is that the "maybe_interesting" member of 'struct
>> type_and_oid_list' is not initialized to '1'. This member was added in
>> 6333e7ae0b (path-walk: mark trees and blobs as UNINTERESTING,
>> 2024-12-20) in a way to help when creating packfiles for a small commit
>> range using the sparse path algorithm (enabled by pack.useSparse=true).
>>
>> The idea here is that the list is marked as "maybe_interesting" if an
>> object is added that does not have the UNINITERSTING flag on it. Later,
> 
> s/UNINITERSTING/UNINTERESTING/

>> this is checked again in case all objects in the list were marked
>> UNINTERESTING after that point in time. In this case, the algorithm
>> skips the list as there is no reason to visit it.
>>
>> This leads to the problem where the "maybe_interesting" member was not
>> appropriately initialized when the list is created from pending objects.
>> This is the fix for now.
>>
>> To help avoid this from happening in the future, a follow-up change will
>> make initializing lists use a shared method instead of allowing for an
>> update to this initialization process to miss some existing copies.
> 
> Yeah, I wanted to say that this feels quite fragile to me and very easy
> to miss. Does this mechanism buy us a lot of performance in the first
> place? Because if not we might as well just remove it entirely.