scalar: verify that we can use a GVFS-enabled repository

Azure Repos does not support partial clones at the moment, but it does
support the GVFS protocol. To that end, the Microsoft fork of Git has a
`gvfs-helper` command that is optionally used to perform essentially the
same functionality as partial clone.

Let's verify that `scalar clone` detects that situation and enables the
GVFS helper.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

t/t9099-scalar.sh

@@ -132,4 +132,141 @@ test_expect_success UNZIP 'scalar diagnose' '
 	grep "^Total: [1-9]" out
 '
 
+GIT_TEST_ALLOW_GVFS_VIA_HTTP=1
+export GIT_TEST_ALLOW_GVFS_VIA_HTTP
+
+test_set_port GIT_TEST_GVFS_PROTOCOL_PORT
+HOST_PORT=127.0.0.1:$GIT_TEST_GVFS_PROTOCOL_PORT
+PID_FILE="$(pwd)"/pid-file.pid
+SERVER_LOG="$(pwd)"/OUT.server.log
+
+test_atexit '
+	test -f "$PID_FILE" || return 0
+
+	# The server will shutdown automatically when we delete the pid-file.
+	rm -f "$PID_FILE"
+
+	test -z "$verbose$verbose_log" || {
+		echo "server log:"
+		cat "$SERVER_LOG"
+	}
+
+	# Give it a few seconds to shutdown (mainly to completely release the
+	# port before the next test start another instance and it attempts to
+	# bind to it).
+	for k in $(test_seq 5)
+	do
+		grep -q "Starting graceful shutdown" "$SERVER_LOG" &&
+		return 0 ||
+		sleep 1
+	done
+
+	echo "stop_gvfs_protocol_server: timeout waiting for server shutdown"
+	return 1
+'
+
+start_gvfs_enabled_http_server () {
+	GIT_HTTP_EXPORT_ALL=1 \
+	test-gvfs-protocol --verbose \
+		--listen=127.0.0.1 \
+		--port=$GIT_TEST_GVFS_PROTOCOL_PORT \
+		--reuseaddr \
+		--pid-file="$PID_FILE" \
+		2>"$SERVER_LOG" &
+
+	for k in 0 1 2 3 4
+	do
+		if test -f "$PID_FILE"
+		then
+			return 0
+		fi
+		sleep 1
+	done
+	return 1
+}
+
+test_expect_success 'start GVFS-enabled server' '
+	git config uploadPack.allowFilter false &&
+	git config uploadPack.allowAnySHA1InWant false &&
+	start_gvfs_enabled_http_server
+'
+
+test_expect_success '`scalar clone` with GVFS-enabled server' '
+	: the fake cache server requires fake authentication &&
+	git config --global core.askPass true &&
+	scalar clone --single-branch -- http://$HOST_PORT/ using-gvfs &&
+
+	: verify that the shared cache has been configured &&
+	cache_key="url_$(printf "%s" http://$HOST_PORT/ |
+		tr A-Z a-z |
+		test-tool sha1)" &&
+	echo "$(pwd)/using-gvfs/.scalarCache/$cache_key" >expect &&
+	git -C using-gvfs/src config gvfs.sharedCache >actual &&
+	test_cmp expect actual &&
+
+	second=$(git rev-parse --verify second:second.t) &&
+	(
+		cd using-gvfs/src &&
+		test_path_is_missing 1/2 &&
+		GIT_TRACE=$PWD/trace.txt git cat-file blob $second >actual &&
+		: verify that the gvfs-helper was invoked to fetch it &&
+		test_i18ngrep gvfs-helper trace.txt &&
+		echo "second" >expect &&
+		test_cmp expect actual
+	)
+'
+
+test_expect_success '`scalar register` parallel to worktree' '
+	git init test-repo/src &&
+	mkdir -p test-repo/out &&
+	scalar register test-repo/out &&
+	git config --get --global --fixed-value \
+		maintenance.repo "$(pwd)/test-repo/src" &&
+	scalar list >scalar.repos &&
+	grep -F "$(pwd)/test-repo/src" scalar.repos &&
+	scalar delete test-repo
+'
+
+test_expect_success '`scalar register` & `unregister` with existing repo' '
+	git init existing &&
+	scalar register existing &&
+	git config --get --global --fixed-value \
+		maintenance.repo "$(pwd)/existing" &&
+	scalar list >scalar.repos &&
+	grep -F "$(pwd)/existing" scalar.repos &&
+	scalar unregister existing &&
+	test_must_fail git config --get --global --fixed-value \
+		maintenance.repo "$(pwd)/existing" &&
+	scalar list >scalar.repos &&
+	! grep -F "$(pwd)/existing" scalar.repos
+'
+
+test_expect_success '`scalar unregister` with existing repo, deleted .git' '
+	scalar register existing &&
+	rm -rf existing/.git &&
+	scalar unregister existing &&
+	test_must_fail git config --get --global --fixed-value \
+		maintenance.repo "$(pwd)/existing" &&
+	scalar list >scalar.repos &&
+	! grep -F "$(pwd)/existing" scalar.repos
+'
+
+test_expect_success '`scalar register` existing repo with `src` folder' '
+	git init existing &&
+	mkdir -p existing/src &&
+	scalar register existing/src &&
+	scalar list >scalar.repos &&
+	grep -F "$(pwd)/existing" scalar.repos &&
+	scalar unregister existing &&
+	scalar list >scalar.repos &&
+	! grep -F "$(pwd)/existing" scalar.repos
+'
+
+test_expect_success '`scalar delete` with existing repo' '
+	git init existing &&
+	scalar register existing &&
+	scalar delete existing &&
+	test_path_is_missing existing
+'
+
 test_done