Enable file logging by default on desktops to help with troubleshooting

- Use the `.log` file extension (recognized on Windows out of the box)
  to better hint that generated files are logs. Some editors provide
  dedicated syntax highlighting for those files.
- Use an underscore to separate the basename from the date and
  the date from the time in log filenames. This makes the filename
  easier to read.
- Keep only 5 log files by default to decrease disk usage in case
  messages are spammed.

core/io/logger.cpp

@@ -152,7 +152,7 @@ void RotatedFileLogger::rotate_file() {
 			char timestamp[21];
 			OS::Date date = OS::get_singleton()->get_date();
 			OS::Time time = OS::get_singleton()->get_time();
-			sprintf(timestamp, "-%04d-%02d-%02d-%02d-%02d-%02d", date.year, date.month, date.day, time.hour, time.min, time.sec);
+			sprintf(timestamp, "_%04d-%02d-%02d_%02d-%02d-%02d", date.year, date.month, date.day, time.hour, time.min, time.sec);
 
 			String backup_name = base_path.get_basename() + timestamp;
 			if (base_path.get_extension() != String()) {

doc/classes/ProjectSettings.xml

@@ -802,10 +802,12 @@
 		<member name="logging/file_logging/enable_file_logging" type="bool" setter="" getter="" default="false">
 			If [code]true[/code], logs all output to files.
 		</member>
-		<member name="logging/file_logging/log_path" type="String" setter="" getter="" default="&quot;user://logs/log.txt&quot;">
+		<member name="logging/file_logging/enable_file_logging.pc" type="bool" setter="" getter="" default="true">
+		</member>
+		<member name="logging/file_logging/log_path" type="String" setter="" getter="" default="&quot;user://logs/godot.log&quot;">
 			Path to logs within the project. Using an [code]user://[/code] path is recommended.
 		</member>
-		<member name="logging/file_logging/max_log_files" type="int" setter="" getter="" default="10">
+		<member name="logging/file_logging/max_log_files" type="int" setter="" getter="" default="5">
 			Specifies the maximum amount of log files allowed (used for rotation).
 		</member>
 		<member name="memory/limits/message_queue/max_size_kb" type="int" setter="" getter="" default="1024">

main/main.cpp

@@ -954,8 +954,13 @@ Error Main::setup(const char *execpath, int argc, char *argv[], bool p_second_ph
 #endif
 
 	GLOBAL_DEF("logging/file_logging/enable_file_logging", false);
-	GLOBAL_DEF("logging/file_logging/log_path", "user://logs/log.txt");
-	GLOBAL_DEF("logging/file_logging/max_log_files", 10);
+	// Only file logging by default on desktop platforms as logs can't be
+	// accessed easily on mobile/Web platforms (if at all).
+	// This also prevents logs from being created for the editor instance, as feature tags
+	// are disabled while in the editor (even if they should logically apply).
+	GLOBAL_DEF("logging/file_logging/enable_file_logging.pc", true);
+	GLOBAL_DEF("logging/file_logging/log_path", "user://logs/godot.log");
+	GLOBAL_DEF("logging/file_logging/max_log_files", 5);
 	ProjectSettings::get_singleton()->set_custom_property_info("logging/file_logging/max_log_files", PropertyInfo(Variant::INT, "logging/file_logging/max_log_files", PROPERTY_HINT_RANGE, "0,20,1,or_greater")); //no negative numbers
 	if (FileAccess::get_create_func(FileAccess::ACCESS_USERDATA) && GLOBAL_GET("logging/file_logging/enable_file_logging")) {
 		String base_path = GLOBAL_GET("logging/file_logging/log_path");