Re: [PATCH] revision: ignore non-existent objects in resolve-undo list

From: Junio C Hamano <gitster@pobox.com>
Date: Oct 18, 2022, 16:40 UTC
Message-ID: <xmqqbkq9ulum.fsf@gitster.g>
In-Reply-To: <xmqqfsflum70.fsf@gitster.g>

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

Show 10 quoted lines

>> Fix the error by emitting a warning when the resolve-undo list mentions
>> objects that do not exist and then ignoring the nonexistent object.
>
> ... this approach is about.  I think it is backwards to sweep the
> problem under the rug without fixing the underlying problem.
>
> We should instead be removing the reference that is no longer even
> usable for the purpose of resolve-undo, e.g. when "rerere forget
> <pathspec>" reads from the resolve-undo extension to recreate the
> conflicts.

Ah, I take half of it back.  "instead" -> "in addition".

The patch corresponds to revision.c::handle_one_reflog_commit() that skips the object referenced by a reflog entry that no longer exists as part of the solution to the same problem as "reflog --stale-fix" solved, and needs to be an integral half of the solution to the "older gc lose blobs referenced by resolve-undo extension" problem.

And the patch goes in the right direction. It is a bit sad that it now has to do parse_object() but in the normal case, the object referenced should be a blob that exists, for which the cost of parsing it would be none (just setting .parsed member to true), so it should be OK.

Thanks.  Will queue.