Re: [PATCH] transport-helper: enforce atomic in push_refs_with_push

> Teach transport-helper how to notice if skipping a ref during push would
> violate atomicity on the client side. We notice that a ref would be
> rejected, and choose not to send it, but don't notice that if the client
> has asked for --atomic we are violating atomicity if all the other
> pushes we are sending would succeed. Asking the server end to uphold
> atomicity wouldn't work here as the server doesn't have any idea that we
> tried to update a ref that's broken.
>
> The added test-case is a succinct way to reproduce this issue that fails
> today. The same steps work fine when we aren't using a transport-helper
> to get to the upstream, i.e. when we've added a local repository as a
> remote:
>
>   git remote add ~/upstream upstream
>
> Signed-off-by: Emily Shaffer <emilyshaffer@google.com>
> ---
>  t/t5541-http-push-smart.sh | 58 ++++++++++++++++++++++++++++++++++++++
>  transport-helper.c         |  6 ++++
>  transport.c                | 15 +++++++++-
>  3 files changed, 78 insertions(+), 1 deletion(-)
>
> diff --git a/t/t5541-http-push-smart.sh b/t/t5541-http-push-smart.sh
> index 8ef8763e06..b57f6d480f 100755
> --- a/t/t5541-http-push-smart.sh
> +++ b/t/t5541-http-push-smart.sh
> @@ -177,6 +177,64 @@ test_expect_success 'push (chunked)' '
>  	 test $HEAD = $(git rev-parse --verify HEAD))
>  '
>  
> +test_expect_success 'push --atomic also prevents branch creation' '
> +	# Make up/master
> +	d=$HTTPD_DOCUMENT_ROOT_PATH/atomic-branches.git &&
> +	git init --bare "$d" &&
> +	git --git-dir="$d" config http.receivepack true &&
> +	up="$HTTPD_URL"/smart/atomic-branches.git &&
> +	test_commit atomic1 &&
> +	test_commit atomic2 &&
> +	git push "$up" master &&
> +	# Make master incompatible with up/master
> +	git reset --hard HEAD^ &&
> +	# Add a new branch
> +	git branch atomic &&
> +	# --atomic should roll back creation of up/atomic
> +	test_must_fail git push --atomic "$up" master atomic &&
> +	git ls-remote "$up" >up-remotes &&
> +	test_must_fail grep atomic up-remotes

> +'
> +
> +test_expect_success 'push --atomic shows all failed refs' '
> +	# Make up/master, up/allrefs
> +	d=$HTTPD_DOCUMENT_ROOT_PATH/atomic-failed-refs.git &&
> +	git init --bare "$d" &&
> +	git --git-dir="$d" config http.receivepack true &&
> +	up="$HTTPD_URL"/smart/atomic-failed-refs.git &&
> +	test_commit allrefs1 &&
> +	test_commit allrefs2 &&
> +	git branch allrefs &&
> +	git push "$up" master allrefs &&
> +	# Make master and allrefs incompatible with up/master, up/allrefs
> +	git checkout allrefs &&
> +	git reset --hard HEAD^ &&
> +	git checkout master &&
> +	git reset --hard HEAD^ &&
> +	# --atomic should complain about both master and allrefs
> +	test_must_fail git push --atomic "$up" master allrefs >&output &&

> +	grep master output &&
> +	grep allrefs output
> +'
> +
> +test_expect_success 'push --atomic indicates collateral failures' '
> +	# Make up/master, up/collateral
> +	d=$HTTPD_DOCUMENT_ROOT_PATH/atomic-collateral.git &&
> +	git init --bare "$d" &&
> +	git --git-dir="$d" config http.receivepack true &&
> +	up="$HTTPD_URL"/smart/atomic-collateral.git &&
> +	test_commit collateral1 &&
> +	test_commit collateral2 &&
> +	git branch collateral &&
> +	git push "$up" master collateral &&
> +	# Make master incompatible with up/master
> +	git reset --hard HEAD^ &&
> +	# --atomic should mention collateral was OK but failed anyway
> +	test_must_fail git push --atomic "$up" master collateral >&output &&