Subject: Re: [PATCH 2/3] send-pack: fix push nego. when remote has refs

From: Emily Shaffer <[email-masked]>
Date: Tue, 13 Jul 2021 15:30:56 -0700

On Wed, Jun 23, 2021 at 03:30:52PM -0700, Jonathan Tan wrote:
> 
> Commit 477673d6f3 ("send-pack: support push negotiation", 2021-05-05)
> did not test the case in which a remote advertises at least one ref. In
> such a case, "remote_refs" in get_commons_through_negotiation() in
> send-pack.c would also contain those refs with a zero ref->new_oid (in
> addition to the refs being pushed with a nonzero ref->new_oid). Passing
> them as negotiation tips to "git fetch" causes an error, so filter them
> out.

So here we are filtering those redundant refs on the client side?

> 
> (The exact error that would happen in "git fetch" in this case is a
> segmentation fault, which is unwanted. This will be fixed in the
> subsequent commit.)
> 
> Signed-off-by: Jonathan Tan <[email-masked]>
> ---
>  send-pack.c           | 6 ++++--
>  t/t5516-fetch-push.sh | 5 +++++
>  2 files changed, 9 insertions(+), 2 deletions(-)
> 
> diff --git a/send-pack.c b/send-pack.c
> index 9cb9f71650..85945becf0 100644
> --- a/send-pack.c
> +++ b/send-pack.c
> @@ -425,8 +425,10 @@ static void get_commons_through_negotiation(const char *url,
>  	child.no_stdin = 1;
>  	child.out = -1;
>  	strvec_pushl(&child.args, "fetch", "--negotiate-only", NULL);
> -	for (ref = remote_refs; ref; ref = ref->next)
> -		strvec_pushf(&child.args, "--negotiation-tip=%s", oid_to_hex(&ref->new_oid));
> +	for (ref = remote_refs; ref; ref = ref->next) {
> +		if (!is_null_oid(&ref->new_oid))
> +			strvec_pushf(&child.args, "--negotiation-tip=%s", oid_to_hex(&ref->new_oid));
> +	}
>  	strvec_push(&child.args, url);
>  
>  	if (start_command(&child))
> diff --git a/t/t5516-fetch-push.sh b/t/t5516-fetch-push.sh
> index 5ce32e531a..e383ba662f 100755
> --- a/t/t5516-fetch-push.sh
> +++ b/t/t5516-fetch-push.sh
> @@ -201,6 +201,7 @@ test_expect_success 'push with negotiation' '
>  	# Without negotiation
>  	mk_empty testrepo &&
>  	git push testrepo $the_first_commit:refs/remotes/origin/first_commit &&
> +	test_commit -C testrepo unrelated_commit &&
>  	git -C testrepo config receive.hideRefs refs/remotes/origin/first_commit &&
>  	echo now pushing without negotiation &&
>  	GIT_TRACE2_EVENT="$(pwd)/event" git -c protocol.version=2 push testrepo refs/heads/main:refs/remotes/origin/main &&
> @@ -210,6 +211,7 @@ test_expect_success 'push with negotiation' '
>  	rm event &&
>  	mk_empty testrepo &&
>  	git push testrepo $the_first_commit:refs/remotes/origin/first_commit &&
> +	test_commit -C testrepo unrelated_commit &&

So now we are asking 'testrepo' to initially advertise that it also has
unrelated_commit, which we don't care about, and expect to work fine
anyway. Ok.

>  	git -C testrepo config receive.hideRefs refs/remotes/origin/first_commit &&
>  	GIT_TRACE2_EVENT="$(pwd)/event" git -c protocol.version=2 -c push.negotiate=1 push testrepo refs/heads/main:refs/remotes/origin/main &&
>  	grep_wrote 2 event # 1 commit, 1 tree
> @@ -219,6 +221,7 @@ test_expect_success 'push with negotiation proceeds anyway even if negotiation f
>  	rm event &&
>  	mk_empty testrepo &&
>  	git push testrepo $the_first_commit:refs/remotes/origin/first_commit &&
> +	test_commit -C testrepo unrelated_commit &&
>  	git -C testrepo config receive.hideRefs refs/remotes/origin/first_commit &&
>  	GIT_TEST_PROTOCOL_VERSION=0 GIT_TRACE2_EVENT="$(pwd)/event" \
>  		git -c push.negotiate=1 push testrepo refs/heads/main:refs/remotes/origin/main 2>err &&
> @@ -1783,6 +1786,7 @@ test_expect_success 'http push with negotiation' '
>  	# Without negotiation
>  	test_create_repo "$SERVER" &&
>  	test_config -C "$SERVER" http.receivepack true &&
> +	test_commit -C "$SERVER" unrelated_commit &&
>  	git -C client push "$URI" first_commit:refs/remotes/origin/first_commit &&
>  	git -C "$SERVER" config receive.hideRefs refs/remotes/origin/first_commit &&
>  	GIT_TRACE2_EVENT="$(pwd)/event" git -C client -c protocol.version=2 \
> @@ -1794,6 +1798,7 @@ test_expect_success 'http push with negotiation' '
>  	rm -rf "$SERVER" &&
>  	test_create_repo "$SERVER" &&
>  	test_config -C "$SERVER" http.receivepack true &&
> +	test_commit -C "$SERVER" unrelated_commit &&
>  	git -C client push "$URI" first_commit:refs/remotes/origin/first_commit &&
>  	git -C "$SERVER" config receive.hideRefs refs/remotes/origin/first_commit &&
>  	GIT_TRACE2_EVENT="$(pwd)/event" git -C client -c protocol.version=2 -c push.negotiate=1 \
> -- 
> 2.32.0.288.g62a8d224e6-goog

Seems reasonable enough to me.
Reviewed-by: Emily Shaffer <[email-masked]>