[PATCH v2 5/8] tests: add a special setup where for protocol.version

["Ævar Arnfjörð Bjarmason" <avarab@gmail.com>]

Add a GIT_TEST_PROTOCOL_VERSION=X test mode which is equivalent to
running with protocol.version=X. This is needed to spot regressions
and differences such as "ls-refs" behaving differently with
transfer.hideRefs. See
https://public-inbox.org/git/20181211104236.GA6899@sigill.intra.peff.net/
for a fix for that regression.

With this all tests pass with GIT_TEST_PROTOCOL_VERSION=0, but fail
with GIT_TEST_PROTOCOL_VERSION=[1|2]. That's OK since this is a new
test mode, subsequent patches will fix up these test failures.

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
---
 protocol.c               | 13 ++++++++++++-
 t/README                 |  6 ++++++
 t/t0410-partial-clone.sh |  3 ++-
 t/t5516-fetch-push.sh    |  3 ++-
 t/t5700-protocol-v1.sh   |  1 +
 t/t5702-protocol-v2.sh   |  1 +
 6 files changed, 24 insertions(+), 3 deletions(-)

diff --git a/protocol.c b/protocol.c
index 5e636785d1..aa06c3b5bc 100644
--- a/protocol.c
+++ b/protocol.c
@@ -17,7 +17,18 @@ static enum protocol_version parse_protocol_version(const char *value)
 enum protocol_version get_protocol_version_config(void)
 {
 	const char *value;
-	if (!git_config_get_string_const("protocol.version", &value)) {
+	const char *git_test_k = "GIT_TEST_PROTOCOL_VERSION";
+	const char *git_test_v = getenv(git_test_k);
+
+	if (git_test_v && strlen(git_test_v)) {
+		enum protocol_version version = parse_protocol_version(git_test_v);
+
+		if (version == protocol_unknown_version)
+			die("unknown value for %s: %s", git_test_k,
+			    git_test_v);
+
+		return version;
+	} else if (!git_config_get_string_const("protocol.version", &value)) {
 		enum protocol_version version = parse_protocol_version(value);
 
 		if (version == protocol_unknown_version)
diff --git a/t/README b/t/README
index 28711cc508..89629c5818 100644
--- a/t/README
+++ b/t/README
@@ -311,6 +311,12 @@ 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=<'protocol.version' config value>, when set,
+runs the test suite with the given protocol.version. E.g. "0", "1" or
+"2". Can be set to the empty string within tests themselves (e.g. "env
+GIT_TEST_PROTOCOL_VERSION= <cmd>") to unset the value in the
+environment as a workaround for "env --unset" not being portable.
+
 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/t0410-partial-clone.sh b/t/t0410-partial-clone.sh
index ba3887f178..8ba3d9b5ab 100755
--- a/t/t0410-partial-clone.sh
+++ b/t/t0410-partial-clone.sh
@@ -178,7 +178,8 @@ test_expect_success 'fetching of missing objects works with ref-in-want enabled'
 
 	rm -rf repo/.git/objects/* &&
 	rm -f trace &&
-	GIT_TRACE_PACKET="$(pwd)/trace" git -C repo cat-file -p "$HASH" &&
+	GIT_TRACE_PACKET="$(pwd)/trace" env GIT_TEST_PROTOCOL_VERSION= \
+		git -C repo cat-file -p "$HASH" &&
 	grep "git< fetch=.*ref-in-want" trace
 '
 
diff --git a/t/t5516-fetch-push.sh b/t/t5516-fetch-push.sh
index 37e8e80893..08cdee0b95 100755
--- a/t/t5516-fetch-push.sh
+++ b/t/t5516-fetch-push.sh
@@ -1187,7 +1187,8 @@ test_expect_success 'fetch exact SHA1 in protocol v2' '
 
 	# fetching the hidden object succeeds by default
 	# NEEDSWORK: should this match the v0 behavior instead?
-	git -C child fetch -v ../testrepo $the_commit:refs/heads/copy
+	env GIT_TEST_PROTOCOL_VERSION= \
+		git -C child fetch -v ../testrepo $the_commit:refs/heads/copy
 '
 
 for configallowtipsha1inwant in true false
diff --git a/t/t5700-protocol-v1.sh b/t/t5700-protocol-v1.sh
index ba86a44eb1..e4d375c462 100755
--- a/t/t5700-protocol-v1.sh
+++ b/t/t5700-protocol-v1.sh
@@ -8,6 +8,7 @@ TEST_NO_CREATE_REPO=1
 
 # Test protocol v1 with 'git://' transport
 #
+unset GIT_TEST_PROTOCOL_VERSION
 . "$TEST_DIRECTORY"/lib-git-daemon.sh
 start_git_daemon --export-all --enable=receive-pack
 daemon_parent=$GIT_DAEMON_DOCUMENT_ROOT_PATH/parent
diff --git a/t/t5702-protocol-v2.sh b/t/t5702-protocol-v2.sh
index 0f2b09ebb8..d1549f294e 100755
--- a/t/t5702-protocol-v2.sh
+++ b/t/t5702-protocol-v2.sh
@@ -8,6 +8,7 @@ TEST_NO_CREATE_REPO=1
 
 # Test protocol v2 with 'git://' transport
 #
+unset GIT_TEST_PROTOCOL_VERSION
 . "$TEST_DIRECTORY"/lib-git-daemon.sh
 start_git_daemon --export-all --enable=receive-pack
 daemon_parent=$GIT_DAEMON_DOCUMENT_ROOT_PATH/parent
-- 
2.20.0.405.gbc1bbc6f85