Flatten a directory structure by one level, preserving the full path of file names

flatten

#!/bin/bash 
set -eu -o pipefail 

# Turn:
#   foo/
#   ├── bar/
#   │   ├── one.txt
#   │   ├── two.txt
#   ├── baz/
#   ├── three.txt
# Into:
#   foo-bar/
#   ├── one.txt
#   ├── two.txt
#   foo-baz/
#   foo-baz-three.txt

DIR=$1

if [ ! -d "$DIR" ]; then 
  >&2 echo "ERR: Not a directory: $DIR"
  exit 1
fi

find "${DIR}" -maxdepth 1 -mindepth 1 -type d -exec sh -c 'new=$(echo "{}" | tr "/" "-" | tr " " "_"); mv -iv -- "{}" "$new"' \;

find "${DIR}" -maxdepth 1 -mindepth 1 -type f -exec sh -c 'new=$(echo "{}" | tr "/" "-" | tr " " "_"); mv -iv -- "{}" "$new"' \;

rmdir -v "${DIR}"