Scripts I wrote that I use all the time

I keep meaning to generalize this (directory target, multiple sources, flags), but I get quite a bit of mileage out of this `unmv` script even as it is:

  #!/bin/sh
  if test "$#" != 2
  then
      echo 'Error: unmv must have exactly 2 arguments'
      exit 1
  fi
  exec mv "$2" "$1"