Make no libusb build clearer

BUILDING.md

@@ -8,7 +8,7 @@ git submodule update --init lib/mbedtls
 
 You also need to install `libusb-1.0` if you want to use the USB functionality.
 
-> If libusb-1.0 is not installed, picotool still builds, but it omits all options that deal with managing a pico via USB (load, save, erase, verify, reboot). Builds that do not include USB support can be recognized because these commands won't appear in the output of the help command. The build output message 'libUSB is not found - no USB support will be built' also appears in the build logs.
+> If libusb-1.0 is not installed, picotool still builds, but it omits all options that deal with managing a pico via USB (load, save, erase, verify, reboot). Builds that do not include USB support can be identified by running `picotool version`, which will state `This version of picotool was compiled without USB support. Some commands are not available.`. Additionally, the unsupported commands won't appear in the output of the help command, and if you attempt to execute an invalid command you will get an error message. The build output message `libUSB is not found - no USB support will be built` also appears in the build logs.
 
 ### Linux / macOS
 

main.cpp

@@ -114,6 +114,10 @@ static const string rp2350_arm_s_family_name = "rp2350-arm-s";
 static const string rp2350_arm_ns_family_name = "rp2350-arm-ns";
 static const string rp2350_riscv_family_name = "rp2350-riscv";
 
+#if !HAS_LIBUSB
+static const string built_without_libusb_message = "\nThis version of picotool was compiled without USB support. Some commands are not available.\n";
+#endif
+
 static string hex_string(int64_t value, int width=8, bool prefix=true, bool uppercase=false) {
     std::stringstream ss;
     if (prefix) ss << "0x";
@@ -705,7 +709,11 @@ struct info_command : public cmd {
     }
 
     string get_doc() const override {
+        #if HAS_LIBUSB
         return "Display information from the target device(s) or file.\nWithout any arguments, this will display basic information for all connected RP-series devices in BOOTSEL mode";
+        #else
+        return "Display information from the target file.";
+        #endif
     }
 };
 
@@ -736,7 +744,11 @@ struct config_command : public cmd {
     }
 
     string get_doc() const override {
+        #if HAS_LIBUSB
         return "Display or change program configuration settings from the target device(s) or file.";
+        #else
+        return "Display or change program configuration settings from the target file.";
+        #endif
     }
 };
 
@@ -1376,8 +1388,12 @@ struct version_command : public cmd {
     bool execute(device_map &devices) override {
         if (settings.version.semantic)
             std::cout << PICOTOOL_VERSION << "\n";
-        else
+        else {
             std::cout << "picotool v" << PICOTOOL_VERSION << " (" << SYSTEM_VERSION << ", " << COMPILER_INFO << ")\n";
+            #if !HAS_LIBUSB
+            std::cout << built_without_libusb_message;
+            #endif
+        }
         if (!settings.version.version.empty()) {
             string picotool_v = string(PICOTOOL_VERSION);
             picotool_v = picotool_v.substr(0, picotool_v.find("-"));
@@ -1623,6 +1639,9 @@ int parse(const int argc, char **argv) {
             } else {
                 fos << string("Use \"picotool help ").append(selected_cmd->name()).append("\" for more info\n");
             }
+            #if !HAS_LIBUSB
+            fos << built_without_libusb_message;
+            #endif
         } else {
             cli::option_map options;
             selected_cmd->get_cli().get_option_help("", "", options);
@@ -1654,6 +1673,11 @@ int parse(const int argc, char **argv) {
             fos.hanging_indent(0);
             fos.wrap_hard();
             fos << "Use \"picotool help <cmd>\" for more info\n";
+            #if !HAS_LIBUSB
+            if (!help_mode) {
+                fos << built_without_libusb_message;
+            }
+            #endif
         }
         fos.flush();
     };