Script to detect additive-only backup files and remove redundant copies.

addonly.sh

#!/usr/bin/env sh

trap 'rm -f "$TMPDIR"/*.addonly' INT EXIT

last=
lastf=
for curr; do
	prev="$last"
	last="$curr"
	>&2 echo -n "$curr "
	if [ "$FILTER" = "" ]; then
		currf="$curr"
	else
		currf="$(mktemp --suffix=.addonly)"
		<"$curr" $FILTER >"$currf"
		echo -n "[$(wc -l "$currf")] "
	fi
	prevf="$lastf"
	lastf="$currf"
	if [ "$prev" = "" ]; then
		>&2 echo "(initial)"
		continue
	fi
	line=$("${GIT:=git}" diff --no-index --numstat "$prevf" "$currf" 2>/dev/null)
	adds=$(echo $line | awk '{ print $1 }')
	dels=$(echo $line | awk '{ print $2 }')
	>&2 echo "(+$adds -$dels)"
	if [ $dels -eq 0 ] && [ $adds -gt 0 ]; then
		echo "rm '$prev'"
	fi
done