optiboot_atmega328-Mini.hex is stale to old version

https://github.com/arduino/Arduino/blob/master/hardware/arduino/avr/bootloaders/optiboot/optiboot_atmega328-Mini.hex is "stale."

This .hex file seems to be from a VERY old version of optiboot, that seems to have been left behind back when the first Uno patches were made (~2012) It's not a target that is supported in the current makefiles, doesn't contain a version number, has bugs that have long since been fixed, and thus is occasionally causing confusion. ( https://github.com/Optiboot/optiboot/issues/219 )

Boards.txt still points at this, but it's not clear how it's different than the normal optiboot .hex file (aside from being old and buggy. Different or no "startup blink", perhaps?) Otherwise I'd recommend deleting it entirely. The boards.txt file also has an incorrect value for the mini upload size using this bootloader.

Compare hardware/arduino/avr/bootloaders/optiboot/optiboot_atmega328-Mini.hex with the current optiboot outputs and inspect boards.txt references for the Mini upload size. First determine whether the Mini target has a distinct supported configuration or should use the normal bootloader. Done means resolving the stale file and correcting or removing its boards.txt references.

Written by the indexing model from the issue text.