README.md fix for git submodule sync & --version / --help (#45)

* add instructions to do `git` submodule sync

* `--help` and `--version`

Author: jamylak

QUICKSTART.md

@@ -2,6 +2,11 @@
 
 Go from zero to your first shader in minutes.
 
+## 0) Populate submodules
+```sh
+git submodule update --init --recursive
+```
+
 ## 1) Install + Build
 
 ### macOS (Homebrew)

README.md

@@ -75,6 +75,7 @@ sudo apt-get install -y \
 ### Linux/macOS
 ```sh
 # FFmpeg is optional; set `-DDISABLE_FFMPEG=ON` (see `CMakeLists.txt`) to build without it.
+git submodule update --init --recursive
 cmake -B build .
 cmake --build build
 ./build/vsdf {filepath}.frag
@@ -83,6 +84,7 @@ cmake --build build
 ### Windows
 ```powershell
 # FFmpeg is optional; set `-DDISABLE_FFMPEG=ON` (see `CMakeLists.txt`) to build without it.
+git submodule update --init --recursive
 cmake -B build -DCMAKE_TOOLCHAIN_FILE="C:/path/to/vcpkg/scripts/buildsystems/vcpkg.cmake" .
 cmake --build build --config Release
 .\build\Release\vsdf.exe {filepath}.frag
@@ -176,6 +178,7 @@ Also by running the test suite it will check this automatically
 
 ### Linux/macOS
 ```sh
+git submodule update --init --recursive
 cmake -B build -DBUILD_TESTS=ON -DDEBUG=ON
 cmake --build build
 ./build/tests/vsdf_tests
@@ -184,6 +187,7 @@ cmake --build build
 
 ### Windows
 ```powershell
+git submodule update --init --recursive
 cmake -B build -DBUILD_TESTS=ON -DCMAKE_BUILD_TYPE=Debug -DCMAKE_TOOLCHAIN_FILE="C:/path/to/vcpkg/scripts/buildsystems/vcpkg.cmake" .
 cmake --build build --config Debug
 .\build\tests\vsdf_tests\Debug\vsdf_tests.exe

src/main.cpp

@@ -8,11 +8,22 @@
 #include <cstdint>
 #include <filesystem>
 #include <optional>
+#include <spdlog/fmt/fmt.h>
 #include <spdlog/spdlog.h>
 #include <string>
 #include <unordered_map>
 
 namespace {
+constexpr const char kVersion[] = "vsdf dev";
+
+void printHelp(const char *exe) {
+    fmt::print("Usage: {} [options] <shader.frag>\nExample: {} --toy "
+               "shaders/testtoyshader.frag\n",
+               exe, exe);
+}
+
+void printVersion() { fmt::print("{}\n", kVersion); }
+
 spdlog::level::level_enum parseLogLevel(const std::string &levelStr) {
     static const std::unordered_map<std::string, spdlog::level::level_enum>
         kLevels = {{"trace", spdlog::level::trace},
@@ -55,7 +66,13 @@ int main(int argc, char **argv) {
     std::string arg;
     for (int i = 1; i < argc; ++i) {
         arg = argv[i];
-        if (arg == "--toy") {
+        if (arg == "--help") {
+            printHelp(argv[0]);
+            return 0;
+        } else if (arg == "--version") {
+            printVersion();
+            return 0;
+        } else if (arg == "--toy") {
             useToyTemplate = true;
             continue;
         } else if (arg == "--headless") {