Merge #6708

6708: Add logappend setting r=heinrich5991 a=def-

To append to log file instead of overwriting it. To use you can create an autoexec_client.cfg with:
```
logfile "client.log"
logappend 1
```
I'm not sure if it should be the default.

## Checklist

- [x] Tested the change ingame
- [ ] Provided screenshots if it is a visual change
- [x] Tested in combination with possibly related configuration options
- [ ] Written a unit test (especially base/) or added coverage to integration test
- [ ] Considered possible null pointers and out of bounds array indexing
- [ ] Changed no physics that affect existing maps
- [ ] Tested the change with [ASan+UBSan or valgrind's memcheck](https://github.com/ddnet/ddnet/#using-addresssanitizer--undefinedbehavioursanitizer-or-valgrinds-memcheck) (optional)


Co-authored-by: Dennis Felsing <dennis@felsin9.de>

src/engine/client/client.cpp

@@ -4774,9 +4774,10 @@ int main(int argc, const char **argv)
 	}
 
 	log_set_loglevel((LEVEL)g_Config.m_Loglevel);
+	const int Mode = g_Config.m_Logappend ? IOFLAG_APPEND : IOFLAG_WRITE;
 	if(g_Config.m_Logfile[0])
 	{
-		IOHANDLE Logfile = pStorage->OpenFile(g_Config.m_Logfile, IOFLAG_WRITE, IStorage::TYPE_SAVE_OR_ABSOLUTE);
+		IOHANDLE Logfile = pStorage->OpenFile(g_Config.m_Logfile, Mode, IStorage::TYPE_SAVE_OR_ABSOLUTE);
 		if(Logfile)
 		{
 			pFutureFileLogger->Set(log_logger_file(Logfile));

src/engine/server/main.cpp

@@ -170,9 +170,10 @@ int main(int argc, const char **argv)
 	pConsole->Register("sv_rescue", "", CFGFLAG_SERVER, CServer::ConRescue, pConsole, "Allow /rescue command so players can teleport themselves out of freeze (setting only works in initial config)");
 
 	log_set_loglevel((LEVEL)g_Config.m_Loglevel);
+	const int Mode = g_Config.m_Logappend ? IOFLAG_APPEND : IOFLAG_WRITE;
 	if(g_Config.m_Logfile[0])
 	{
-		IOHANDLE Logfile = pStorage->OpenFile(g_Config.m_Logfile, IOFLAG_WRITE, IStorage::TYPE_SAVE_OR_ABSOLUTE);
+		IOHANDLE Logfile = pStorage->OpenFile(g_Config.m_Logfile, Mode, IStorage::TYPE_SAVE_OR_ABSOLUTE);
 		if(Logfile)
 		{
 			pFutureFileLogger->Set(log_logger_file(Logfile));

src/engine/shared/config_variables.h

@@ -12,6 +12,7 @@ MACRO_CONFIG_INT(PlayerCountry, player_country, -1, -1, 1000, CFGFLAG_SAVE | CFG
 MACRO_CONFIG_STR(Password, password, 32, "", CFGFLAG_CLIENT | CFGFLAG_SERVER | CFGFLAG_NONTEEHISTORIC, "Password to the server")
 MACRO_CONFIG_STR(Logfile, logfile, 128, "", CFGFLAG_SAVE | CFGFLAG_CLIENT | CFGFLAG_SERVER, "Filename to log all output to")
 MACRO_CONFIG_INT(Loglevel, loglevel, 2, 0, 4, CFGFLAG_SAVE | CFGFLAG_CLIENT | CFGFLAG_SERVER, "Log level (0 = Error, 1 = Warn, 2 = Info, 3 = Debug, 4 = Trace)")
+MACRO_CONFIG_INT(Logappend, logappend, 1, 0, 1, CFGFLAG_SAVE | CFGFLAG_CLIENT | CFGFLAG_SERVER, "Append to logfile instead of overwriting it every time")
 MACRO_CONFIG_INT(ConsoleOutputLevel, console_output_level, 0, 0, 2, CFGFLAG_SAVE | CFGFLAG_CLIENT | CFGFLAG_SERVER, "Adjusts the amount of information in the console")
 MACRO_CONFIG_INT(ConsoleEnableColors, console_enable_colors, 1, 0, 1, CFGFLAG_SAVE | CFGFLAG_CLIENT | CFGFLAG_SERVER, "Enable colors in console output")
 MACRO_CONFIG_INT(Events, events, 1, 0, 1, CFGFLAG_SAVE | CFGFLAG_CLIENT | CFGFLAG_SERVER, "Enable triggering of events, (eye emotes on some holidays in server, christmas skins in client).")