行頭下げ.UTF-8/LFにのみ対応.ファイルの末尾に改行必須。

indenter.sh

#!/bin/bash

array=("　" "「" "『")

formatted=""

while read -r line; do
  if [ -n "$line" ] && [[ ! " ${array[*]} " =~ " "${line::1}" " ]]; then
    formatted+="　"
  fi
  formatted+=$line
  formatted+=$'\n'
done <"$1"

echo "$formatted" | sed '${/^$/d;}' >"$1"