degesch: add a /nick command

Somehow I've missed it entirely.

degesch.c

@@ -3663,6 +3663,18 @@ handle_command_list (struct app_context *ctx, char *arguments)
 	return true;
 }
 
+static bool
+handle_command_nick (struct app_context *ctx, char *arguments)
+{
+	if (!server_command_check (ctx, "change nickname"))
+		return true;
+	if (!*arguments)
+		return false;
+
+	irc_send (ctx, "NICK %s", cut_word (&arguments));
+	return true;
+}
+
 static bool
 handle_command_quote (struct app_context *ctx, char *arguments)
 {
@@ -3725,8 +3737,10 @@ g_command_handlers[] =
 	{ "motd",    NULL, "", "" },
 	{ "away",    NULL, "", "" },
 #endif
+	{ "nick",    handle_command_nick,   "Change current nick",
+	  "<nickname>" },
 	{ "quote",   handle_command_quote,  "Send a raw command to the server",
-	  "command" },
+	  "<command>" },
 };
 
 static bool