reproduce:
        # apt-get install sparse
        # sparse version: v0.6.4-66-g0196afe1
        # https://github.com/koverstreet/bcachefs/commit/ed76395059b49ba846b70861b3fac6ded3b8596d
        git remote add koverstreet-bcachefs https://github.com/koverstreet/bcachefs
        git fetch --no-tags koverstreet-bcachefs bcachefs-testing
        git checkout ed76395059b49ba846b70861b3fac6ded3b8596d
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        make W=1 C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__ -fmax-errors=unlimited -fmax-warnings=unlimited' O=build_dir ARCH=x86_64 olddefconfig
        make W=1 C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__ -fmax-errors=unlimited -fmax-warnings=unlimited' O=build_dir ARCH=x86_64 SHELL=/bin/bash fs/bcachefs/