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/partition.cpp

@@ -69,11 +69,15 @@ void validate(boost::any &v, const std::vector<std::string> &values, MaxCellSize
     v = boost::any(MaxCellSizesArgument{output});
 }
 
-return_code parseArguments(int argc, char *argv[], partition::PartitionConfig &config)
+return_code
+parseArguments(int argc, char *argv[], std::string &verbosity, partition::PartitionConfig &config)
 {
     // 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");
+    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());
 
     // declare a group of options that will be allowed both on command line
     boost::program_options::options_description config_options("Configuration");
@@ -184,9 +188,10 @@ return_code parseArguments(int argc, char *argv[], partition::PartitionConfig &c
 int main(int argc, char *argv[]) try
 {
     util::LogPolicy::GetInstance().Unmute();
+    std::string verbosity;
     partition::PartitionConfig partition_config;
 
-    const auto result = parseArguments(argc, argv, partition_config);
+    const auto result = parseArguments(argc, argv, verbosity, partition_config);
 
     if (return_code::fail == result)
     {
@@ -198,6 +203,8 @@ int main(int argc, char *argv[]) try
         return EXIT_SUCCESS;
     }
 
+    util::LogPolicy::GetInstance().SetLevel(verbosity);
+
     // set the default in/output names
     partition_config.UseDefaultOutputNames(partition_config.base_path);