Re: [PATCH 1/8] tests: define GIT_TEST_PROTOCOL_VERSION

> Define a GIT_TEST_PROTOCOL_VERSION environment variable meant to be used
> from tests. When set, this ensures protocol.version is at least the
> given value, allowing the entire test suite to be run as if this
> configuration is in place for all repositories.
>
> As of this patch, all tests pass whether GIT_TEST_PROTOCOL_VERSION is
> unset, set to 0, or set to 1. Some tests fail when
> GIT_TEST_PROTOCOL_VERSION is set to 2, but this will be dealt with in
> subsequent patches.
>
> This is based on work by Ævar Arnfjörð Bjarmason.
>
> Signed-off-by: Jonathan Tan <jonathantanmy@google.com>
> ---
>  protocol.c                  | 17 +++++++++++++++--
>  t/README                    |  3 +++
>  t/t5400-send-pack.sh        |  2 +-
>  t/t5551-http-fetch-smart.sh |  3 ++-
>  4 files changed, 21 insertions(+), 4 deletions(-)
>
> diff --git a/protocol.c b/protocol.c
> index 5664bd7a05..c7a735bfa2 100644
> --- a/protocol.c
> +++ b/protocol.c
> @@ -42,6 +42,10 @@ static const char *format_protocol_version(enum protocol_version version)
>  enum protocol_version get_protocol_version_config(void)
>  {
>  	const char *value;
> +	enum protocol_version retval = protocol_v0;
> +	const char *git_test_k = "GIT_TEST_PROTOCOL_VERSION";
> +	const char *git_test_v = getenv(git_test_k);
> +
>  	if (!git_config_get_string_const("protocol.version", &value)) {
>  		enum protocol_version version = parse_protocol_version(value);
>
> @@ -49,10 +53,19 @@ enum protocol_version get_protocol_version_config(void)
>  			die("unknown value for config 'protocol.version': %s",
>  			    value);
>
> -		return version;
> +		retval = version;
> +	}
> +
> +	if (git_test_v && strlen(git_test_v)) {
> +		enum protocol_version env = parse_protocol_version(git_test_v);
> +
> +		if (env == protocol_unknown_version)
> +			die("unknown value for %s: %s", git_test_k, git_test_v);
> +		if (retval < env)
> +			retval = env;
>  	}
>
> -	return protocol_v0;
> +	return retval;
>  }
>
>  void register_allowed_protocol_version(enum protocol_version version)
> diff --git a/t/README b/t/README
> index 25864ec883..21e941eb94 100644
> --- a/t/README
> +++ b/t/README
> @@ -327,6 +327,9 @@ marked strings" in po/README for details.
>  GIT_TEST_SPLIT_INDEX=<boolean> forces split-index mode on the whole
>  test suite. Accept any boolean values that are accepted by git-config.
>
> +GIT_TEST_PROTOCOL_VERSION=<n>, when set, overrides the
> +'protocol.version' setting to n if it is less than n.
> +

>  GIT_TEST_FULL_IN_PACK_ARRAY=<boolean> exercises the uncommon
>  pack-objects code path where there are more than 1024 packs even if
>  the actual number of packs in repository is below this limit. Accept
> diff --git a/t/t5400-send-pack.sh b/t/t5400-send-pack.sh
> index f1932ea431..571d620aed 100755
> --- a/t/t5400-send-pack.sh
> +++ b/t/t5400-send-pack.sh
> @@ -288,7 +288,7 @@ test_expect_success 'receive-pack de-dupes .have lines' '
>  	$shared .have
>  	EOF
>
> -	GIT_TRACE_PACKET=$(pwd)/trace \
> +	GIT_TRACE_PACKET=$(pwd)/trace GIT_TEST_PROTOCOL_VERSION= \
>  	    git push \
>  		--receive-pack="unset GIT_TRACE_PACKET; git-receive-pack" \
>  		fork HEAD:foo &&
> diff --git a/t/t5551-http-fetch-smart.sh b/t/t5551-http-fetch-smart.sh
> index a60dd907bd..8f620e0a35 100755
> --- a/t/t5551-http-fetch-smart.sh
> +++ b/t/t5551-http-fetch-smart.sh
> @@ -44,7 +44,8 @@ test_expect_success 'clone http repository' '
>  	< Cache-Control: no-cache, max-age=0, must-revalidate
>  	< Content-Type: application/x-git-upload-pack-result
>  	EOF
> -	GIT_TRACE_CURL=true git clone --quiet $HTTPD_URL/smart/repo.git clone 2>err &&
> +	GIT_TRACE_CURL=true GIT_TEST_PROTOCOL_VERSION= \
> +		git clone --quiet $HTTPD_URL/smart/repo.git clone 2>err &&
>  	test_cmp file clone/file &&
>  	tr '\''\015'\'' Q <err |
>  	sed -e "