Control log level via -v option

Allow the user to control the log level via the conventional `-v`
command line option. Multiplying this option-as per convention-increases
the verbosity.

This is an additional way to set the log level, in addition to the
existing:
- environment variable
- build type (debug vs release)

Given it is the most intentional and direct way to set the log level it
has precedence over all other options.

src/UserOpt.cpp

@@ -28,6 +28,9 @@ UserOpt::UserOpt(int argc, char** argv) {
   TCLAP::ValueArg<fs::path> arg_outfile
     {"o", "out", "Out <file-or-path>", false, fs::path{}, "A path on the filesystem", cmd};
 
+  TCLAP::MultiSwitchArg arg_verbose
+    {"v", "verbose", "Verbosity level", cmd, 0};
+
   TCLAP::UnlabeledMultiArg<fs::path> arg_paths
     {"files", "Archive(s) to extract or file(s) to compress", true, "A path on the filesystem", cmd};
   // clang-format on
@@ -38,6 +41,7 @@ UserOpt::UserOpt(int argc, char** argv) {
   if (arg_extract.isSet()) this->extract = arg_extract.getValue();
   if (arg_outfile.isSet()) this->out = arg_outfile.getValue();
 
+  this->verbosity = arg_verbose.getValue();
   this->interactive = arg_extract.getValue();
 
   if (arg_paths.isSet()) {

src/UserOpt.hpp

@@ -13,6 +13,7 @@ struct UserOpt {
   optional<bool> compress;
   optional<bool> extract;
   bool interactive;
+  int verbosity;
   std::optional<fs::path> out;
   std::set<fs::path> paths;
 

src/main.cpp

@@ -14,8 +14,9 @@ using namespace std;
 
 int main(int argc, char** argv) {
   log::init();
-
   UserOpt user_opt = UserOpt{argc, argv};
+  log::init(user_opt.verbosity);
+
   try {
     unique_ptr<UserIntent> user_intent = make_intent(user_opt);
     user_intent->execute();

src/util/Log.hpp

@@ -1,6 +1,7 @@
 #pragma once
 #include <spdlog/common.h>
 #include <spdlog/spdlog.h>
+
 #include <cstdlib>
 #ifdef NDEBUG
 #define XWIM_LOGLEVEL SPDLOG_LEVEL_ERROR
@@ -57,7 +58,27 @@ spdlog::level::level_enum _init_from_compile() {
  * The determined level is then set for the default logger via
  * `spdlog::set_level`.
  */
-void init(spdlog::level::level_enum level = spdlog::level::level_enum::off) {
+void init(int verbosity = -1,
+          spdlog::level::level_enum level = spdlog::level::level_enum::off) {
+  if (verbosity != -1) {
+    switch (verbosity) {
+      case 0:
+        spdlog::set_level(spdlog::level::off);
+        break;
+      case 1:
+        spdlog::set_level(spdlog::level::info);
+        break;
+      case 2:
+        spdlog::set_level(spdlog::level::debug);
+        break;
+      case 3:
+      default:
+        spdlog::set_level(spdlog::level::trace);
+        break;
+    }
+    return;
+  }
+
   if (spdlog::level::level_enum::off != level) {
     spdlog::set_level(level);
     return;