gvfs: verify that the built-in FSMonitor is disabled

When using a virtual file system layer, the FSMonitor does not make
sense.

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

t/t1093-virtualfilesystem.sh

@@ -368,4 +368,15 @@ test_expect_success 'folder with same prefix as file' '
 	test_cmp expected actual
 '
 
+test_expect_success MINGW,FSMONITOR_DAEMON 'virtualfilesystem hook disables built-in FSMonitor' '
+	clean_repo &&
+	test_config core.usebuiltinfsmonitor true &&
+	write_script .git/hooks/virtualfilesystem <<-\EOF &&
+		printf "dir1/\0"
+	EOF
+	git config core.virtualfilesystem .git/hooks/virtualfilesystem &&
+	git status &&
+	test_must_fail git fsmonitor--daemon status
+'
+
 test_done