Subject: Re: [PATCH] t/t7700-repack.sh: fix test breakages with `GIT_TEST_MULTI_PACK_INDEX=1`

From: Junio C Hamano <[email-masked]>
Date: Tue, 02 Apr 2024 11:37:10 -0700

Taylor Blau <[email-masked]> writes:

> There are a handful of related test breakages which are found when
> running t/t7700-repack.sh with GIT_TEST_MULTI_PACK_INDEX set to "1" in
> your environment.
>
> Both test failures are the result of something like:
>
>     git repack --write-midx --write-bitmap-index [...] &&
>
>     test_path_is_file $midx &&
>     test_path_is_file $midx-$(midx_checksum $objdir).bitmap
>
> , where we repack instructing Git to write a new MIDX and corresponding
> MIDX bitamp.
>
> The error occurs when GIT_TEST_MULTI_PACK_INDEX=1 is found in the
> enviornment. This causes Git to write out a second MIDX (after
> processing the builtin's `--write-midx` argument) which is identical to
> the first, but does not request a bitmap (since we did not set the
> GIT_TEST_MULTI_PACK_INDEX_WRITE_BITMAP variable in the environment).

Doesn't it sound more like a bug, though?  If a command line option
requests something, should we still be honoring a contradicting
instruction given by environment variable(s)?

But anyway.

> diff --git a/t/t7700-repack.sh b/t/t7700-repack.sh
> index 94f9f4a1da..127efe99f8 100755
> --- a/t/t7700-repack.sh
> +++ b/t/t7700-repack.sh
> @@ -629,6 +629,7 @@ test_expect_success '--write-midx with preferred bitmap tips' '
>  		git log --format="create refs/tags/%s/%s %H" HEAD >refs &&
>  		git update-ref --stdin <refs &&
>  
> +		GIT_TEST_MULTI_PACK_INDEX=0 \
>  		git repack --write-midx --write-bitmap-index &&
>  		test_path_is_file $midx &&
>  		test_path_is_file $midx-$(midx_checksum $objdir).bitmap &&

Is it a viable alternative approach to skip this check (and the
other one) when GIT_TEST_MULTI_PACK_INDEX is set (i.e., lazy
prereq).  It will give us a better documentation value, e.g.,

	test_lazy_prereq FORCED_MIDX '
                # Features that are broken when GIT_TEST_* forces it
                # to enable are protexted with this prerequisite.
		test "$GIT_TEST_MULTI_PACK_INDEX" = 1;
	'

	test_expect_success !FORCED_MIDX '--write-midx with ...' '
		...
	'

With a single comment, we can annotate any future tests that relies
on features working correctly even with GIT_TEST_MULTI_PACK_INDEX.