Re: [PATCH] t7701: make annotated tag unreachable

[Jeff King <peff@peff.net>]

On Wed, Jun 21, 2023 at 06:21:10AM -0400, Taylor Blau wrote:

> But after pruning, that object is kept around for two reasons. One, the
> tag object's mtime wasn't adjusted to be beyond the 1-hour cutoff, so it
> would be kept as due to its recency regardless. The other reason is
> because the tag itself is reachable.
> 
> Use mktag to write the tag object directly without pointing a reference
> at it, and adjust the mtime of the tag object to be older than the
> cutoff to ensure that our `gc.recentObjectsHook` configuration is
> working as intended.

Thanks, this should fix the problem (which you can notice by making the
recentObjectsHook in the test a noop and seeing that it still passes).

But there's one more thing...

> diff --git a/t/t7701-repack-unpack-unreachable.sh b/t/t7701-repack-unpack-unreachable.sh
> index ba428c18a8..ceb4e805d2 100755
> --- a/t/t7701-repack-unpack-unreachable.sh
> +++ b/t/t7701-repack-unpack-unreachable.sh
> @@ -126,8 +126,19 @@ test_expect_success 'gc.recentObjectsHook' '
>  	git cat-file -p $obj2 &&
>  	git cat-file -p $obj3 &&
> 
> +	# make an unreachable annotated tag object to ensure we rescue objects
> +	# which are reachable from non-pruned unreachable objects
>  	git tag -a -m tag obj2-tag $obj2 &&
> -	obj2_tag="$(git rev-parse obj2-tag)" &&
> +	obj2_tag="$(git mktag <<-EOF
> +	object $obj2
> +	type blob
> +	tag obj2-tag
> +	tagger T A Gger <tagger@example.com> 1234567890 -0000
> +	EOF
> +	)" &&

Since we are using "mktag" here, the call to "git tag" can go away
entirely. It's not only redundant, but it erroneously keeps reachability
to $obj2. The test still does something useful (it makes sure that
$obj2_tag was saved), but it is failing to test what it wanted to about
$obj2, namely that it is kept because the hook mentioned an object that
points to it.

So we'd want to squash in:

diff --git a/t/t7701-repack-unpack-unreachable.sh b/t/t7701-repack-unpack-unreachable.sh
index ceb4e805d2..fe6c3e77a3 100755
--- a/t/t7701-repack-unpack-unreachable.sh
+++ b/t/t7701-repack-unpack-unreachable.sh
@@ -128,7 +128,6 @@ test_expect_success 'gc.recentObjectsHook' '
 
 	# make an unreachable annotated tag object to ensure we rescue objects
 	# which are reachable from non-pruned unreachable objects
-	git tag -a -m tag obj2-tag $obj2 &&
 	obj2_tag="$(git mktag <<-EOF
 	object $obj2
 	type blob

-Peff