Add a -s command line option for specifying session name

src/main.cc

@@ -178,15 +178,15 @@ int kakoune(memoryview<String> params)
 {
     ParametersParser parser(params, { { "c", true },
                                       { "e", true },
-                                      { "n", false } });
+                                      { "n", false },
-
+                                      { "s", true } });
     String init_command;
     if (parser.has_option("e"))
         init_command = parser.option_value("e");
 
     if (parser.has_option("c"))
     {
-        for (auto opt : { "n" })
+        for (auto opt : { "n", "s" })
         {
             if (parser.has_option(opt))
             {
@@ -236,7 +236,7 @@ int kakoune(memoryview<String> params)
         write_debug("pid: " + to_string(getpid()));
         write_debug("utf-8 test: é á ï");
 
-        Server server;
+        Server server(parser.has_option("s") ? parser.option_value("s") : to_string(getpid()));
 
         if (not parser.has_option("n")) try
         {

src/remote.cc

@@ -508,8 +508,8 @@ private:
     FDWatcher m_socket_watcher;
 };
 
-Server::Server()
+Server::Server(const String& session_name)
-    : m_filename{"/tmp/kak-" + to_string(getpid())}
+    : m_filename{"/tmp/kak-" + session_name}
 {
     int listen_sock = socket(AF_UNIX, SOCK_STREAM, 0);
     fcntl(listen_sock, F_SETFD, FD_CLOEXEC);

src/remote.hh

@@ -32,7 +32,7 @@ std::unique_ptr<RemoteClient> connect_to(const String& pid,
 
 struct Server : public Singleton<Server>
 {
-    Server();
+    Server(const String& session_name);
     ~Server();
     const String& filename() const { return m_filename; }