Add a kill command that kills the current session

Fixes #331
A given session can be killed with 'echo kill | kak -p <session>'

src/client_manager.cc

@@ -13,7 +13,12 @@ namespace Kakoune
 {
 
 ClientManager::ClientManager() = default;
-ClientManager::~ClientManager() = default;
+ClientManager::~ClientManager()
+{
+    // So that clients destructor find the client manager empty
+    // so that local UI does not fork.
+    ClientList clients = std::move(m_clients);
+}
 
 String ClientManager::generate_name() const
 {

src/commands.cc

@@ -263,6 +263,17 @@ const CommandDesc writeall_cmd = {
     [](const ParametersParser&, Context&){ write_all_buffers(); }
 };
 
+const CommandDesc kill_cmd = {
+    "kill",
+    nullptr,
+    "kill current session, quit all clients and server",
+    no_params,
+    CommandFlags::None,
+    CommandHelper{},
+    CommandCompleter{},
+    [](const ParametersParser&, Context&){ throw kill_session{}; }
+};
+
 template<bool force>
 void quit()
 {
@@ -1649,6 +1660,7 @@ void register_commands()
     register_command(writeall_cmd);
     register_command(writeall_quit_cmd);
     register_command(quit_cmd);
+    register_command(kill_cmd);
     register_command(force_quit_cmd);
     register_command(write_quit_cmd);
     register_command(force_write_quit_cmd);

src/commands.hh

@@ -12,6 +12,8 @@ class Key;
 void register_commands();
 void exec_keys(ConstArrayView<Key> keys, Context& context);
 
+struct kill_session {};
+
 }
 
 #endif // commands_hh_INCLUDED

src/main.cc

@@ -450,6 +450,8 @@ int run_server(StringView session, StringView init_command,
     if (not daemon)
         create_local_client(create_local_ui(dummy_ui), init_command, startup_error);
 
+    try
+    {
         while (not terminate and (not client_manager.empty() or daemon))
         {
             client_manager.redraw_clients();
@@ -458,6 +460,8 @@ int run_server(StringView session, StringView init_command,
             buffer_manager.clear_buffer_trash();
             string_registry.purge_unused();
         }
+    }
+    catch (const kill_session&) {}
 
     {
         Context empty_context{Context::EmptyContextFlag{}};