Add 'session' command to change remote session name

src/commands.cc

@@ -1895,6 +1895,25 @@ const CommandDesc change_working_directory_cmd = {
     }
 };
 
+const CommandDesc change_session_name = {
+    "session",
+    nullptr,
+    "session <name>: change remote session name",
+    ParameterDesc{{}, ParameterDesc::Flags::None, 1, 1},
+    CommandFlags::None,
+    CommandHelper{},
+    CommandCompleter{},
+    [](const ParametersParser& parser, Context&, const ShellContext&)
+    {
+        if (not Server::instance().rename_session(parser[0]))
+            throw runtime_error(format("Cannot rename current session: '{}' may be already in use", parser[0]));
+
+        // update modeline
+        for (auto& client : ClientManager::instance())
+            client->redraw_ifn();
+    }
+};
+
 }
 
 void register_commands()
@@ -1952,6 +1971,7 @@ void register_commands()
     register_command(set_register_cmd);
     register_command(select_cmd);
     register_command(change_working_directory_cmd);
+    register_command(change_session_name);
 }
 
 }

src/remote.cc

@@ -651,13 +651,26 @@ Server::Server(String session_name)
     m_listener.reset(new FDWatcher{listen_sock, accepter});
 }
 
+bool Server::rename_session(const String& name)
+{
+    String old_socket_file = format("/tmp/kakoune/{}/{}", getpwuid(geteuid())->pw_name, m_session);
+    String new_socket_file = format("/tmp/kakoune/{}/{}", getpwuid(geteuid())->pw_name, name);
+
+    if (link(old_socket_file.c_str(), new_socket_file.c_str()) != 0)
+        return false;
+
+    unlink(old_socket_file.c_str());
+
+    m_session = name;
+    return true;
+}
+
 void Server::close_session(bool do_unlink)
 {
     if (do_unlink)
     {
-        char socket_file[128];
-        format_to(socket_file, "/tmp/kakoune/{}/{}", getpwuid(geteuid())->pw_name, m_session);
-        unlink(socket_file);
+        String socket_file = format("/tmp/kakoune/{}/{}", getpwuid(geteuid())->pw_name, m_session);
+        unlink(socket_file.c_str());
     }
     m_listener->close_fd();
     m_listener.reset();

src/remote.hh

@@ -48,6 +48,7 @@ struct Server : public Singleton<Server>
     ~Server();
     const String& session() const { return m_session; }
 
+    bool rename_session(const String& name);
     void close_session(bool do_unlink = true);
 
 private: