#!/bin/sh

t=`mktemp`
git log --pretty=raw "$@" > "$t"

allreverted=
reverts()
{
	commit=$1
	reverted=$2
	eval "reverts_in_$commit=\"\$reverts_in_$commit $reverted\""
	eval "reverts_$reverted=\"\$reverts_$reverted $commit\""
	allreverted="$allreverted $reverted"
	#echo >&2 "Found: $commit reverts $reverted"
}

# in the tree of reverters, look for any leaves of even depth

reverters()
{
	eval "echo \$reverts_$1"
}

whatreverts_inverted()
{
	local status reverter printme
	status=false
	printme=true
	for reverter in `reverters "$1"`; do
		if ! whatreverts "$reverter"; then
			status=true
		fi
		printme=false
	done
	if $printme; then
		echo "$1"
	fi
	$status
}

whatreverts()
{
	local status reverter
	status=false
	for reverter in `reverters "$1"`; do
		if ! whatreverts_inverted "$reverter"; then
			status=true
		fi
	done
	$status
}

# pass 1: find which commit reverts which
while IFS= read -r L; do
	case "$L" in
		"commit "*)
			commit="${L#commit }"
			;;
		"    This reverts commit "*)
			reverted=${L#    This reverts commit }
			reverted=${reverted%.}
			reverts "$commit" "$reverted"
			;;
	esac
done < "$t"

# pass 2: for all reverted commits, find their status and their latest revert
for commit in $allreverted; do
	if eval "[ -n \"\$seen_$commit\" ]"; then
		continue
	fi
	eval "seen_$commit=1"
	if eval "[ -n \"\$reverts_in_$commit\" ]"; then
		continue
	fi
	if revertedby=`whatreverts "$commit" | grep .`; then
		echo "$commit got reverted by $revertedby:"
		git log -1 $revertedby
	fi
done

rm -f "$t"