Add --verbosity,-l command line option

Allow to fine-control logging verbosity via command line
and LogPolicy setting (useful when OSRM used as library).

Closes #4299

src/tools/routed.cpp

@@ -68,6 +68,7 @@ static EngineConfig::Algorithm stringToAlgorithm(std::string algorithm)
 // generate boost::program_options object for the routing part
 inline unsigned generateServerProgramOptions(const int argc,
                                              const char *argv[],
+                                             std::string verbosity,
                                              boost::filesystem::path &base_path,
                                              std::string &ip_address,
                                              int &ip_port,
@@ -87,9 +88,12 @@ inline unsigned generateServerProgramOptions(const int argc,
 
     // declare a group of options that will be allowed only on command line
     boost::program_options::options_description generic_options("Options");
-    generic_options.add_options()                                         //
-        ("version,v", "Show version")("help,h", "Show this help message") //
-        ("trial", value<bool>(&trial)->implicit_value(true), "Quit after initialization");
+    generic_options.add_options() //
+        ("version,v", "Show version")("help,h", "Show this help message")(
+            "verbosity,l",
+            boost::program_options::value<std::string>(&verbosity)->default_value("INFO"),
+            std::string("Log verbosity level: " + util::LogPolicy::GetLevels()).c_str())(
+            "trial", value<bool>(&trial)->implicit_value(true), "Quit after initialization");
 
     // declare a group of options that will be allowed on command line
     boost::program_options::options_description config_options("Configuration");
@@ -202,10 +206,12 @@ int main(int argc, const char *argv[]) try
     int ip_port, requested_thread_num;
 
     EngineConfig config;
+    std::string verbosity;
     boost::filesystem::path base_path;
     std::string algorithm;
     const unsigned init_result = generateServerProgramOptions(argc,
                                                               argv,
+                                                              verbosity,
                                                               base_path,
                                                               ip_address,
                                                               ip_port,
@@ -227,6 +233,9 @@ int main(int argc, const char *argv[]) try
     {
         return EXIT_FAILURE;
     }
+
+    util::LogPolicy::GetInstance().SetLevel(verbosity);
+
     if (!base_path.empty())
     {
         config.storage_config = storage::StorageConfig(base_path);