Re: [PATCH 2/5] t6421: add tests checking for excessive object downloads during merge

> +test_expect_merge_algorithm failure failure 'Objects downloaded for single relevant rename' '
> +	test_setup_repo &&
> +	git clone --sparse --filter=blob:none "file://$(pwd)/server" objects-single &&
> +	(
> +		cd objects-single &&
> +
> +		git rev-list --objects --all --missing=print |
> +			grep '\?' >missing-objects-before &&
> +
> +		git checkout -q origin/A &&
> +
> +		GIT_TRACE2_PERF="$(pwd)/trace.output" git -c merge.directoryRenames=true merge --no-stat --no-progress origin/B-single &&

> +
> +		# Check the number of objects we reported we would fetch
> +		cat >expect <<-EOF &&
> +		 ..........fetch_count:2
> +		 ......fetch_count:1

> +		EOF
> +		grep fetch_count trace.output | cut -d "|" -f 9 >actual &&
> +		test_cmp expect actual &&
> +
> +		# Check the number of fetch commands exec-ed
> +		grep d0.*fetch.negotiationAlgorithm trace.output >fetches &&
> +		test_line_count = 2 fetches &&
> +
> +		git rev-list --objects --all --missing=print |
> +			grep ^? >missing-objects-after &&
> +		test_cmp missing-objects-before missing-objects-after |
> +			grep "^[-+]?" >found-and-new-objects &&
> +		# We should not have any NEW missing objects
> +		! grep ^+ found-and-new-objects &&
> +		# Fetched 2+1=3 objects, so should have 3 fewer missing objects
> +		test_line_count = 3 found-and-new-objects
> +	)
> +'