Introduce CLI

main: Parse args using getopt_long() in main().

Begin implementation of a CLI. It can be launched
using ./qswiki config --cli.

Allow connecting to another instance using "attach" command.
This uses Unix domain sockets, and in the future can be used
to drop caches, reload template, etc.

Closes: #21

cliserver.cpp

@@ -0,0 +1,77 @@
+#include <sys/socket.h>
+#include <sys/un.h>
+#include <unistd.h>
+#include "cliserver.h"
+#include "logger.h"
+CLIServer::CLIServer(CLIHandler &handler)
+{
+	this->handler = &handler;
+}
+
+bool CLIServer::detachServer(std::string socketpath)
+{
+	struct sockaddr_un name;
+	const int max_socket_length = sizeof(name.sun_path) - 1;
+	if(socketpath.size() > max_socket_length)
+	{
+		perror("socket path too long");
+		return false;
+	}
+	int s = socket(AF_UNIX, SOCK_DGRAM, 0);
+	if(s == -1)
+	{
+		perror("socket");
+		return false;
+	}
+
+	memset(&name, 0, sizeof(name));
+	name.sun_family = AF_UNIX;
+	memcpy(&name.sun_path, socketpath.c_str(), socketpath.size());
+
+	unlink(socketpath.c_str());
+	int ret = bind(s, (const struct sockaddr *)&name, sizeof(name));
+	if(ret == -1)
+	{
+		perror("bind");
+		exit(EXIT_FAILURE);
+	}
+
+	auto worker = [=]
+	{
+		while(true)
+		{
+			char buffer[1024] = {0};
+			struct sockaddr_un peer;
+			socklen_t peerlen = sizeof(peer);
+
+			int ret = recvfrom(s, buffer, sizeof(buffer) - 1, 0, (struct sockaddr *)&peer, &peerlen);
+			if(ret == -1)
+			{
+				Logger::error() << "Error during recvfrom in CLI server: " << strerror(errno);
+				return false;
+			}
+
+			std::string input{buffer};
+
+			auto pair = CLIHandler::splitCommand(input);
+
+			auto result = handler->processCommand(pair.first, pair.second);
+			char resultCode = '0';
+			if(result.first)
+			{
+				resultCode = '1';
+			}
+			std::string resultString;
+			resultString += resultCode;
+			resultString += result.second;
+			ret = sendto(s, resultString.c_str(), resultString.size(), 0, (struct sockaddr *)&peer, peerlen);
+			if(ret == -1)
+			{
+				Logger::error() << "Error during sendto in CLI server: " << strerror(errno);
+			}
+		}
+	};
+	std::thread t1{worker};
+	t1.detach();
+	return true;
+}