add a --fakechain argument for tests

The core tests use the blockchain, and reset it to be able
to add test data to it. This does not play nice with the
databases, since those will save that data without an explicit
save call.
We add a fakechain flag that the tests will set, which tells
the core and blockchain code to use a separate database, as
well as skip a few things like checkpoints and fixup, which
only make sense for real data.

src/cryptonote_core/cryptonote_core.cpp

@@ -97,7 +97,7 @@ namespace cryptonote
   //-----------------------------------------------------------------------------------------------
   bool core::update_checkpoints()
   {
-    if (m_testnet) return true;
+    if (m_testnet || m_fakechain) return true;
 
     if (m_checkpoints_updating.test_and_set()) return true;
 
@@ -145,18 +145,20 @@ namespace cryptonote
     command_line::add_arg(desc, command_line::arg_db_sync_mode);
     command_line::add_arg(desc, command_line::arg_show_time_stats);
     command_line::add_arg(desc, command_line::arg_db_auto_remove_logs);
+    command_line::add_arg(desc, command_line::arg_fakechain);
   }
   //-----------------------------------------------------------------------------------------------
   bool core::handle_command_line(const boost::program_options::variables_map& vm)
   {
     m_testnet = command_line::get_arg(vm, command_line::arg_testnet_on);
+    m_fakechain = command_line::get_arg(vm, command_line::arg_fakechain);
 
     auto data_dir_arg = m_testnet ? command_line::arg_testnet_data_dir : command_line::arg_data_dir;
     m_config_folder = command_line::get_arg(vm, data_dir_arg);
 
     auto data_dir = boost::filesystem::path(m_config_folder);
 
-    if (!m_testnet)
+    if (!m_testnet && !m_fakechain)
     {
       cryptonote::checkpoints checkpoints;
       if (!cryptonote::create_checkpoints(checkpoints))
@@ -257,6 +259,9 @@ namespace cryptonote
 
     boost::filesystem::path folder(m_config_folder);
 
+    if (m_fakechain)
+      folder /= "fake";
+
     folder /= db->get_db_name();
 
     LOG_PRINT_L0("Loading blockchain from folder " << folder.string() << " ...");
@@ -337,7 +342,7 @@ namespace cryptonote
     m_blockchain_storage.set_user_options(blocks_threads,
         blocks_per_sync, sync_mode, fast_sync);
 
-    r = m_blockchain_storage.init(db, m_testnet);
+    r = m_blockchain_storage.init(db, m_testnet, m_fakechain);
 
     bool show_time_stats = command_line::get_arg(vm, command_line::arg_show_time_stats) != 0;
     m_blockchain_storage.set_show_time_stats(show_time_stats);