geoff-codes

    #!/bin/sh
    here=$PWD
    dir=.
    depth=
    rm -f /tmp/list
    
    [ $# -eq 1 ] &&
      [ -e "$1" ] && dir=$1 || depth=$1 
    
    [ $# -eq 2 ] && for i in "$@"; do
      [ -e "$i" ] && dir=$i || depth=$i
    done
    
    for each in $(find -L $dir -type d -depth $depth 2>/dev/null); do
      [ -x "$each" ] && cd "$each" &&
      sha=$(tar c . 2>/dev/null | tar xmvO 2>&1 | xz | shasum | sed 's| .*||') 
      [ $(find . 2>/dev/null | wc -l) -gt 1 ] && echo $sha $each >> /tmp/list
      cd "$here"
    done
    
    for sha in $(cat /tmp/list | sed 's| .*||' | sort | uniq); do
      [ $(grep $sha /tmp/list | wc -l) -gt 1 ]  &&
        echo Identical directories: && grep $sha /tmp/list | sed 's|.* ||' && echo
    done