Re: [PATCH v3 2/2] Mark 'git cat-file' sparse-index compatible

From: Junio C Hamano <gitster@pobox.com>
Date: Sep 3, 2024, 19:19 UTC
Message-ID: <xmqqle08ilzd.fsf@gitster.g>
In-Reply-To: <f4d1461b99350151970528e12a92290cb65f7860.1725386044.git.gitgitgadget@gmail.com>

"Kevin Lyles via GitGitGadget" <gitgitgadget@gmail.com> writes:

> Subject: Re: [PATCH v3 2/2] Mark 'git cat-file' sparse-index compatible

The same comment on the commit title applies here.

> From: Kevin Lyles <klyles+github@epic.com>
>
> This change affects how 'git cat-file' works with the index when

Again, we start by describing the status quo (e.g. "'git cat-file' always expands a sparse-index to a full index"), explaining why it is undesirable, and hinting what you want to do about it.

And then give an order to the codebase to "become like so".

Show 14 quoted lines

> diff --git a/builtin/cat-file.c b/builtin/cat-file.c
> index 18fe58d6b8b..1afdfb5cbae 100644
> --- a/builtin/cat-file.c
> +++ b/builtin/cat-file.c
> @@ -1047,6 +1047,9 @@ int cmd_cat_file(int argc, const char **argv, const char *prefix)
>  	if (batch.buffer_output < 0)
>  		batch.buffer_output = batch.all_objects;
>  
> +	prepare_repo_settings(the_repository);
> +	the_repository->settings.command_requires_full_index = 0;
> +
>  	/* Return early if we're in batch mode? */
>  	if (batch.enabled) {
>  		if (opt_cw)

How should the correctness of a change line this validated, by the way? By following manually all the code paths from this point and making sure that the access to an element (or size) of the index that is sparsed out is preceded by a lazy rehydration of a tree that represents a subhierarchy in the sparse-index? Addition to end-to-end tests may increase the test coverage, but I am not sure how to ensure the coverage is exhaustive.

Thanks.