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/common/command_line.cpp

@@ -91,4 +91,9 @@ namespace command_line
   , "Show time-stats when processing blocks/txs and disk synchronization."
   , 0
   };
+  const command_line::arg_descriptor<bool> arg_fakechain  = {
+    "fakechain"
+  , "Use a fake chain for testing purposes."
+  , false
+  };
 }

src/common/command_line.h

@@ -215,4 +215,5 @@ namespace command_line
   extern const arg_descriptor<uint64_t> arg_prep_blocks_threads;
   extern const arg_descriptor<uint64_t> arg_db_auto_remove_logs;
   extern const arg_descriptor<uint64_t> arg_show_time_stats;
+  extern const arg_descriptor<bool> arg_fakechain;
 }

src/cryptonote_core/blockchain.cpp

@@ -236,7 +236,7 @@ uint64_t Blockchain::get_current_blockchain_height() const
 //------------------------------------------------------------------
 //FIXME: possibly move this into the constructor, to avoid accidentally
 //       dereferencing a null BlockchainDB pointer
-bool Blockchain::init(BlockchainDB* db, const bool testnet)
+bool Blockchain::init(BlockchainDB* db, const bool testnet, const bool fakechain)
 {
     LOG_PRINT_L3("Blockchain::" << __func__);
     CRITICAL_REGION_LOCAL(m_blockchain_lock);
@@ -293,8 +293,11 @@ bool Blockchain::init(BlockchainDB* db, const bool testnet)
     {
     }
 
+    if (!fakechain)
+    {
       // ensure we fixup anything we found and fix in the future
       m_db->fixup();
+    }
 
     // check how far behind we are
     uint64_t top_block_timestamp = m_db->get_top_block_timestamp();
@@ -311,7 +314,7 @@ bool Blockchain::init(BlockchainDB* db, const bool testnet)
     m_async_pool.create_thread(boost::bind(&boost::asio::io_service::run, &m_async_service));
 
 #if defined(PER_BLOCK_CHECKPOINT)
-    if (m_fast_sync && get_blocks_dat_start(testnet) != nullptr)
+    if (!fakechain && m_fast_sync && get_blocks_dat_start(testnet) != nullptr)
     {
         if (get_blocks_dat_size(testnet) > 4)
         {

src/cryptonote_core/blockchain.h

@@ -91,7 +91,7 @@ namespace cryptonote
 
     Blockchain(tx_memory_pool& tx_pool);
 
-    bool init(BlockchainDB* db, const bool testnet = false);
+    bool init(BlockchainDB* db, const bool testnet = false, const bool fakechain = false);
     bool deinit();
 
     void set_checkpoints(checkpoints&& chk_pts) { m_checkpoints = chk_pts; }

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);

src/cryptonote_core/cryptonote_core.h

@@ -199,6 +199,7 @@ namespace cryptonote
      uint64_t m_target_blockchain_height;
 
      bool m_testnet;
+     bool m_fakechain;
      std::string m_checkpoints_path;
      time_t m_last_dns_checkpoints_update;
      time_t m_last_json_checkpoints_update;

tests/core_tests/chaingen.h

@@ -484,6 +484,10 @@ inline bool do_replay_events(std::vector<test_event_entry>& events)
   if (!r)
     return false;
 
+  // hardcode a --fakechain option for tests
+  static const char * const fakechain[] = {"", "--fakechain"};
+  boost::program_options::store(boost::program_options::parse_command_line(2, fakechain, desc), vm);
+
   cryptonote::cryptonote_protocol_stub pr; //TODO: stub only for this kind of test, make real validation of relayed objects
   cryptonote::core c(&pr);
   // FIXME: make sure that vm has arg_testnet_on set to true or false if