git clone https://github.com/PX4/Bootloader
cd Bootloader/
git submodule sync --recursive
git submodule update --recursive --init
make fmuk66v3_bl
Bootloader/build/fmuk66v3_bl/fmuk66v3_bl.bin
git fetch
git checkout branchname
git pull
git submodule sync --recursive
git submodule update --recursive --init
make fmuk66v3_bl