#!/bin/rc

flag e +

repo=$1
tag=$2
index=$3
out=$4
ifs='
'

fn checkstatus {}

GIT_INDEX_FILE=`{pwd}^/$out.index {
	checkstatus
	git -C $repo read-tree --empty
	git -C $repo update-index --index-info <$index
	tree=`{git -C $repo write-tree} ; checkstatus
	rm $out.index
}
git -C $repo update-ref refs/tags/$tag $tree

if([ -e $out ]) {
	oldtree=`{cat $out} ; checkstatus
	if(~ $tree $oldtree)
		exit 0
}

echo $tree >$out.tmp
mv $out.tmp $out