tools/move-if-change

# Like mv $1 $2, but if the files are the same, just delete $1.
# Status is 0 if $2 is changed, 1 otherwise.

if test -r "$2"; then
  if cmp "$1" "$2" > /dev/null; then
    echo "$2" is unchanged
    rm -f "$1"
  else
    mv -f "$1" "$2"
  fi
else
  mv -f "$1" "$2"
fi