expand

#!/bin/bash

source "$JH_INC/scriptutils.sh" || { echo "Could not load bashlib"; exit 1; }
[ $# -lt 1 ] && echoerrx1 "$0 <Folder>"

Folder=$(rtrim_slash "$1")
chkdir "$Folder"

Output=$Folder/files.txt
find "$Folder" -type f -name "*.m" -o -name "*.cpp" -o -name "*.h" >| "$Output"
for f in $(cat "$Output"); do
    echo "$f"
    expand -t 4 "$f" | sponge "$f"
done