git hook that sets flags according to modified files

post-receive

while read oldrev newrev refname
do
  COMPILE_JAVASCRIPTS=0
  COMPILE_IMAGES=0
  COMPILE_STYLESHEETS=0

  for file in `git diff $oldrev $newrev --name-only`; do
    if [ `echo $file | cut -c 1-22` == "app/assets/javascripts" \
         -o \
         `echo $file | cut -c 1-25` == "shared/assets/javascripts" \
       ]; then
       COMPILE_JAVASCRIPTS=1
    fi
    if [ `echo $file | cut -c 1-17` == "app/assets/images" \
         -o \
         `echo $file | cut -c 1-20` == "shared/assets/images" \
       ]; then
       COMPILE_IMAGES=1
    fi
    if [ `echo $file | cut -c 1-22` == "app/assets/stylesheets" \
         -o \
         `echo $file | cut -c 1-25` == "shared/assets/stylesheets" \
       ]; then
       COMPILE_STYLESHEETS=1
    fi
  done

  # Build options
  OPTIONS="--production"
  if [ $COMPILE_JAVASCRIPTS == 1 ]; then
    OPTIONS="$OPTIONS --javascripts"
  fi
  if [ $COMPILE_IMAGES == 1 ]; then
    OPTIONS="$OPTIONS --images"
  fi
  if [ $COMPILE_STYLESHEETS == 1 ]; then
    OPTIONS="$OPTIONS --stylesheets"
  fi
  echo "OPTIONS: $OPTIONS"
done