Simplify double-nested lambdas in command selection. (#1526)

The lambda 'find_command' was potentially confusable with the function that implements `vcpkg find`. Moreover, the capture of the whole VcpkgCmdArguments when only the desired command name was needed was overkill. The simple for loop is shorter, easier to debug, and avoids needing to form the complicated 'decltype' to return nullptr.

src/vcpkg.cpp

@@ -93,6 +93,21 @@ namespace
         return false;
     }
 
+    template<class CommandRegistrationKind>
+    static const CommandRegistrationKind* choose_command(const std::string& command_name,
+                                                         View<CommandRegistrationKind> command_registrations)
+    {
+        for (const auto& command_registration : command_registrations)
+        {
+            if (Strings::case_insensitive_ascii_equals(command_registration.metadata.name, command_name))
+            {
+                return &command_registration;
+            }
+        }
+
+        return nullptr;
+    }
+
     void inner(const Filesystem& fs, const VcpkgCmdArguments& args, const BundleSettings& bundle)
     {
         // track version on each invocation
@@ -104,24 +119,9 @@ namespace
             Checks::exit_fail(VCPKG_LINE_INFO);
         }
 
-        static const auto find_command = [&](auto&& commands) {
-            auto it = Util::find_if(commands, [&](auto&& commandc) {
-                return Strings::case_insensitive_ascii_equals(commandc.metadata.name, args.get_command());
-            });
-            using std::end;
-            if (it != end(commands))
-            {
-                return &*it;
-            }
-            else
-            {
-                return static_cast<decltype(&*it)>(nullptr);
-            }
-        };
-
         get_global_metrics_collector().track_bool(BoolMetric::DetectedContainer, detect_container(fs));
 
-        if (const auto command_function = find_command(basic_commands))
+        if (const auto command_function = choose_command(args.get_command(), basic_commands))
         {
             get_global_metrics_collector().track_string(StringMetric::CommandName, command_function->metadata.name);
             return command_function->function(args, fs);
@@ -133,7 +133,7 @@ namespace
 
         fs.current_path(paths.root, VCPKG_LINE_INFO);
 
-        if (const auto command_function = find_command(paths_commands))
+        if (const auto command_function = choose_command(args.get_command(), paths_commands))
         {
             get_global_metrics_collector().track_string(StringMetric::CommandName, command_function->metadata.name);
             return command_function->function(args, paths);
@@ -141,7 +141,7 @@ namespace
 
         Triplet default_triplet = vcpkg::default_triplet(args, paths.get_triplet_db());
         Triplet host_triplet = vcpkg::default_host_triplet(args, paths.get_triplet_db());
-        if (const auto command_function = find_command(triplet_commands))
+        if (const auto command_function = choose_command(args.get_command(), triplet_commands))
         {
             get_global_metrics_collector().track_string(StringMetric::CommandName, command_function->metadata.name);
             return command_function->function(args, paths, default_triplet, host_triplet);