Merging 3b/3b+ configs does not enable openGL driver on a fresly installed Raspbian

[jose1711]

merge-config.sh does not update /boot/config.txt on model 3b/3b+ after a fresh Raspbian installation. This appears to be caused by the fact that merge-config.sh does not understand model sections.

This is the stock config:
config_default.txt

Running merge-config.sh performance-tune/raspi-3b-tune.config /boot/config.txt results in kms overlay enabled but only for model 4 ([pi4] section). The default (legacy/non-GL) is used after reboot making stepmania awfully slow.

I also believe that it is not the intention of merge-config.sh script to change commented line as happens currently in this line:

raspbian-stepmania-arcade/merge-config.sh

Line 54 in 63a3d6d

sed -i "s/${KEY} *=.*/${line}/" "${TARGET_CONFIG}"