Util: Add support for stdin and | piping

In order to accomplish this, the arguments have to be stored in the
object. Because () evaluation order is not defined in the spec.

Because arguments have to be stored now, char pointers no longer work
and std::strings are stored instead. Systems object also cant be
returned as a reference anymore because you need to be able to know
which is the lhs and which is the rhs in the operator overloads.

src/util/system.h

@@ -13,7 +13,8 @@ using SplitCallback = std::function<void(size_t, char*)>;
 
 class System {
 public:
-	System() {}
+	System();
+	System(std::vector<std::string> arguments);
 	virtual ~System() {}
 
 	enum FileDescriptor {
@@ -21,22 +22,28 @@ public:
 		WriteFileDescriptor,
 	};
 
-	void operator()(const char* command);
-	void operator()(std::string command);
-	void operator()(std::string_view command);
-	void operator()(const std::vector<const char*>& arguments);
-	void operator()(const std::vector<std::string>& arguments);
-	void operator()(const std::vector<std::string_view>& arguments);
+	System operator()();
+	System operator()(const char* command);
+	System operator()(std::string command);
+	System operator()(std::string_view command);
+	System operator()(const std::vector<const char*>& arguments);
+	System operator()(const std::vector<std::string>& arguments);
+	System operator()(const std::vector<std::string_view>& arguments);
 
+	System operator|(System rhs);
+
+	void print(const std::vector<std::string>& arguments);
+
+	const std::vector<std::string>& arguments() const { return m_arguments; }
 	std::string output() const { return m_output; }
 	std::string error() const { return m_error; }
 	int status() const { return m_status; }
 
 private:
-	void operator()(const std::vector<char*>& arguments);
+	System exec(std::string input = "");
 	void readFromFileDescriptor(int fileDescriptor[2], std::string& output);
-	size_t split(char* split, const char* delimiters, SplitCallback callback = {});
 
+	std::vector<std::string> m_arguments;
 	std::string m_output;
 	std::string m_error;
 	int m_status { 0 };