Subject: Re: [PATCH v2 1/3] t7519: avoid file to index mtime race for untracked cache

From: Junio C Hamano <[email-masked]>
Date: Fri, 25 Feb 2022 11:07:54 -0800

"Tao Klerks via GitGitGadget" <[email-masked]> writes:

> From: Tao Klerks <[email-masked]>
>
> In t7519 there is a test that writes files to disk, and immediately
> writes the untracked index. Because of mtime-comparison logic that

"untracked cache", I think.

> uses a 1-second resolution, this means the cached entries are not
> trusted/used under some circumstances
> (see read-cache.c#is_racy_stat()).
>
> Untracked cache tests in t7063 use a 1-second delay to avoid this
> issue, but we don't want to introduce arbitrary slowdowns, so instead
> use test-tool chmtime to backdate the files slightly.

Good approach.  Perhaps fixing 7063 can be marked as #leftoverbit?

> This change doesn't actually affect the outcome of the test, but does
> enhance its validity, and becomes relevant after later changes.
>
> Signed-off-by: Tao Klerks <[email-masked]>
> ---
>  t/t7519-status-fsmonitor.sh | 6 ++++++
>  1 file changed, 6 insertions(+)
>
> diff --git a/t/t7519-status-fsmonitor.sh b/t/t7519-status-fsmonitor.sh
> index a6308acf006..3f984136ea9 100755
> --- a/t/t7519-status-fsmonitor.sh
> +++ b/t/t7519-status-fsmonitor.sh
> @@ -324,13 +324,19 @@ test_expect_success UNTRACKED_CACHE 'ignore .git changes when invalidating UNTR'
>  		cd dot-git &&
>  		mkdir -p .git/hooks &&
>  		: >tracked &&
> +		test-tool chmtime =-60 tracked &&
>  		: >modified &&
> +		test-tool chmtime =-60 modified &&
>  		mkdir dir1 &&
>  		: >dir1/tracked &&
> +		test-tool chmtime =-60 dir1/tracked &&
>  		: >dir1/modified &&
> +		test-tool chmtime =-60 dir1/modified &&
>  		mkdir dir2 &&
>  		: >dir2/tracked &&
> +		test-tool chmtime =-60 dir2/tracked &&
>  		: >dir2/modified &&
> +		test-tool chmtime =-60 dir2/modified &&
>  		write_integration_script &&
>  		git config core.fsmonitor .git/hooks/fsmonitor-test &&
>  		git update-index --untracked-cache &&