#!/bin/sh
# Thanks to Thomas Rast
# http://thread.gmane.org/gmane.comp.version-control.git/124807

SUBDIRECTORY_OK=1
. "$(git --exec-path)/git-sh-setup"
cd_to_toplevel # for the tar below

pre="${1-HEAD}"
post="$2"

tmp="$(mktemp -d)"

cleanup () {
	rm -rf $tmp
}

trap cleanup EXIT

mkdir "$tmp"/a "$tmp"/b

if [ -n "$post" ]; then
	git diff --name-only "$pre" "$post" > "$tmp"/filelist
	while read name; do
		mkdir -p "$tmp"/b/"$(dirname "$name")"
		git show "$post":"$name" > "$tmp"/b/"$name"
	done < "$tmp"/filelist
else
	git diff --name-only "$pre" > "$tmp"/filelist
	tar -c -T "$tmp"/filelist | (cd "$tmp"/b && tar -x)
fi

while read name; do
	mkdir -p "$tmp"/a/"$(dirname "$name")"
	git show "$pre":"$name" > "$tmp"/a/"$name"
done < "$tmp"/filelist

cd "$tmp"
#meld a b
#diff -ur a b
tool="$(git-config diff.tool)"
if [ -n "$tool" ]; then
  "$tool" a b
else
  diff -urN a b
fi