Re: [PATCH 1/2] [GSOC] cat-file: fix --batch report changed-type bug

[ZheNing Hu <adlternative@gmail.com>]

Jeff King <peff@peff.net> 于2021年6月3日周四 上午4:01写道：
>
> I don't see any inaccuracies there. I do think we could explain it a bit
> more succinctly. I'll give my attempt, and then you can pick and choose
> which parts to include between ours. :)
>

Yes, you wrote it more concisely. I don't need to write out the details of
those variables. I just need to tell the reader the introduction of
skip_object_info will break the assumption of --batch that we have found
the object type.

>   Subject: cat-file: handle trivial --batch format with --batch-all-objects
>
>   The --batch code to print an object assumes we found out the type of
>   the object from calling oid_object_info_extended(). This is true for
>   the default format, but even in a custom format, we manually modify
>   the object_info struct to ask for the type.
>
>   This assumption was broken by 845de33a5b (cat-file: avoid noop calls
>   to sha1_object_info_extended, 2016-05-18). That commit skips the call
>   to oid_object_info_extended() entirely when --batch-all-objects is in
>   use, and the custom format does not include any placeholders that
>   require calling it.
>
>   This results in an error when we try to confirm that the type didn't
>   change:
>
>     $ git cat-file --batch=batman --batch-all-objects
>     batman
>     fatal: object 000023961a0c02d6e21dc51ea3484ff71abf1c74 changed type!?
>
>   and also has other subtle effects (e.g., we'd fail to stream a blob,
>   since we don't realize it's a blog in the first place).
>

s/blog/blob/

>   We can fix this by flipping the order of the setup. The check for "do
>   we need to get the object info" must come _after_ we've decided
>   whether we need to look up the type.
>
> -Peff

Thanks.
--
ZheNing Hu