Re: [PATCH] multi-pack-index: fix --object-dir from outside repo

[Derrick Stolee <stolee@gmail.com>]

On 8/20/2021 3:35 PM, Johannes Berg wrote:
> If using --object-dir to point into a repo, 'write' will
> segfault trying to access the object-dir via the repo it
> found, but that's not fully initialized. Fix it to use
> the object_dir properly.

Thanks for finding this! It's difficult to cover all of
the cases, but I'm glad you found this and added a test.

> +test_expect_success 'multi-pack-index with --object-dir need not be in repo' '
> +	p="$(pwd)" &&
> +	rm -f $objdir/multi-pack-index &&
> +	cd / &&
> +	git multi-pack-index --object-dir="$p/$objdir" write &&
> +	cd "$p"

Why are you using "cd /" here? Even if you mean to use "cd",
please do so within a sub-shell.

Could you instead init a new repo within the current directory
and point the object-dir to that location?

It could look something like this, (warning: I did not test this)

	git init other &&
	test_commit -C other first &&
	git multi-pack-index --object-dir=other/.git/objects write

And is the only post-condition you are checking that we do not
crash? Or is there a specific result you are looking for? For
instance, we can double check that the MIDX was written:

	test_path_is_file other/.git/objects/pack/multi-pack-index

but also you seem to be touching areas that delete files. Could
we 'touch' some of those and then see them get deleted?

Thanks,
-Stolee