rev-parse git command doesn't need the --work-tree argument
rev-parse git command doesn't need the --work-tree argument

small tidyup
JackDanger/rpi-update,vinodpanicker/rpi-update,TwizzyDizzy/rpi-update,c0d3z3r0/rock-update,lurch/rpi-update,Hexxeh/rpi-update,shrx/rpi-update,shaun10/rpi-update,Gouthamve/rpi-update