compileerror

# mkdir smi2021-tree/ && cd smi2021-tree/
# git init
# git config core.sparseCheckout true
# echo drivers/media/usb/smi2021/ >> .git/info/sparse-checkout
# git remote add origin https://github.com/jonjonarnearne/smi2021.git
# git fetch origin --depth=1
# git pull origin smi2021v3-wip
# cd drivers/media/usb/smi2021/
# make -C /lib/modules/$(uname -r)/build M=$PWD

make: Entering directory '/usr/lib/modules/3.18.6-1-ARCH/build'
fatal: Not a git repository (or any of the parent directories): .git
  LD      /tmp/smi2021-tree/drivers/media/usb/smi2021/built-in.o
  Building modules, stage 2.
fatal: Not a git repository (or any of the parent directories): .git
  MODPOST 0 modules
make: Leaving directory '/usr/lib/modules/3.18.6-1-ARCH/build'