Add support for command-line user arguments.

Implements the standard Unix double dash (--) commandline argument:
* Arguments after a double dash (--) are ignored by Godot and stored for the user.
* User can access them via `OS.get_cmdline_user_args()`

Example:

`godot.exe scene_to_run.tscn --fullscreen -- --start-level 2`

4 files changed, 17 insertions, 2 deletions

diff --git a/core/core_bind.cpp b/core/core_bind.cpp
index 3f94ff8329..65cc3b4c42 100644
--- a/core/core_bind.cpp
+++ b/core/core_bind.cpp
@@ -331,6 +331,16 @@ Vector<String> OS::get_cmdline_args() {
 	return cmdlinev;
 }
 
+Vector<String> OS::get_cmdline_user_args() {
+	List<String> cmdline = ::OS::get_singleton()->get_cmdline_user_args();
+	Vector<String> cmdlinev;
+	for (const String &E : cmdline) {
+		cmdlinev.push_back(E);
+	}
+
+	return cmdlinev;
+}
+
 String OS::get_locale() const {
 	return ::OS::get_singleton()->get_locale();
 }
@@ -614,6 +624,7 @@ void OS::_bind_methods() {
 
 	ClassDB::bind_method(D_METHOD("get_name"), &OS::get_name);
 	ClassDB::bind_method(D_METHOD("get_cmdline_args"), &OS::get_cmdline_args);
+	ClassDB::bind_method(D_METHOD("get_cmdline_user_args"), &OS::get_cmdline_user_args);
 
 	ClassDB::bind_method(D_METHOD("delay_usec", "usec"), &OS::delay_usec);
 	ClassDB::bind_method(D_METHOD("delay_msec", "msec"), &OS::delay_msec);
diff --git a/core/core_bind.h b/core/core_bind.h
index 3a4faa3422..8f66dc03ce 100644
--- a/core/core_bind.h
+++ b/core/core_bind.h
@@ -188,6 +188,7 @@ public:
 
 	String get_name() const;
 	Vector<String> get_cmdline_args();
+	Vector<String> get_cmdline_user_args();
 
 	String get_locale() const;
 	String get_locale_language() const;
diff --git a/core/os/os.cpp b/core/os/os.cpp
index 619e3eb06f..1358c926d1 100644
--- a/core/os/os.cpp
+++ b/core/os/os.cpp
@@ -362,9 +362,10 @@ String OS::get_model_name() const {
 	return "GenericDevice";
 }
 
-void OS::set_cmdline(const char *p_execpath, const List<String> &p_args) {
+void OS::set_cmdline(const char *p_execpath, const List<String> &p_args, const List<String> &p_user_args) {
 	_execpath = String::utf8(p_execpath);
 	_cmdline = p_args;
+	_user_args = p_user_args;
 }
 
 String OS::get_unique_id() const {
diff --git a/core/os/os.h b/core/os/os.h
index b9f7328929..9152b797ef 100644
--- a/core/os/os.h
+++ b/core/os/os.h
@@ -46,6 +46,7 @@ class OS {
 	static uint64_t target_ticks;
 	String _execpath;
 	List<String> _cmdline;
+	List<String> _user_args;
 	bool _keep_screen_on = true; // set default value to true, because this had been true before godot 2.0.
 	bool low_processor_usage_mode = false;
 	int low_processor_usage_mode_sleep_usec = 10000;
@@ -106,7 +107,7 @@ protected:
 	virtual void finalize() = 0;
 	virtual void finalize_core() = 0;
 
-	virtual void set_cmdline(const char *p_execpath, const List<String> &p_args);
+	virtual void set_cmdline(const char *p_execpath, const List<String> &p_args, const List<String> &p_user_args);
 
 	virtual bool _check_internal_feature_support(const String &p_feature) = 0;
 
@@ -162,6 +163,7 @@ public:
 
 	virtual String get_name() const = 0;
 	virtual List<String> get_cmdline_args() const { return _cmdline; }
+	virtual List<String> get_cmdline_user_args() const { return _user_args; }
 	virtual List<String> get_cmdline_platform_args() const { return List<String>(); }
 	virtual String get_model_name() const;