Git command to compare size of file in working tree against index/commit

git-cmpsize

#!/bin/bash

if [[ $1 == "--help" || $1 == "-h" ]]; then
    cat <<USAGE
usage: $(basename $0) FILE [REVISION]

Compare file size between version at REVISION (default: index) and
on disk.
USAGE
    exit
fi

SIZE_OLD=$(git show "$2:$1" | wc -c)
SIZE_NEW=$(cat "$1" | wc -c)

REV=${2:-index}
PAD_LENGTH=$(( ${#REV} > 4 ? ${#REV} : 4 ))
PAD_LENGTH=$(( $PAD_LENGTH + $(( $SIZE_OLD > $SIZE_NEW ? ${#SIZE_OLD} : ${#SIZE_NEW} )) ))

printf "Size in $REV: %$(( ${PAD_LENGTH} - ${#REV} ))d\n" "$SIZE_OLD"
printf "Size on file: %$(( ${PAD_LENGTH} - 4 ))d\n" "$SIZE_NEW"
printf "Difference:   %+$(( ${PAD_LENGTH} - 4 ))d\n" "$(( $SIZE_NEW - $SIZE_OLD ))"