#!/bin/sh

usage () {
	echo "usage:" $@
	exit 127
}

die () {
	echo $@
	exit 128
}

if test $# -lt 2 || test $# -gt 3
then
	usage "$0 <repository> <new_workdir> [<branch>]"
fi

orig_git=$1
new_workdir=$2
branch=$3

# want to make sure that what is pointed to has a .git directory ...
test -d "$orig_git/.git" || die "\"$orig_git\" is not a git repository!"

# don't link to a workdir
if test -L "$orig_git/.git/config"
then
	die "\"$orig_git\" is a working directory only, please specify" \
		"a complete repository."
fi

# make sure the the links use full paths
orig_git=$(cd "$orig_git"; pwd)

# create the workdir
mkdir -p "$new_workdir/.git" || die "unable to create \"$new_workdir\"!"

# create the links to the original repo.  explictly exclude index, HEAD and
# logs/HEAD from the list since they are purely related to the current working
# directory, and should not be shared.
for x in config refs logs/refs objects info hooks packed-refs remotes rr-cache
do
	case $x in
	*/*)
		mkdir -p "$(dirname "$new_workdir/.git/$x")"
		;;
	esac
	ln -s "$orig_git/.git/$x" "$new_workdir/.git/$x"
done

# now setup the workdir
cd "$new_workdir"
# copy the HEAD from the original repository as a default branch
cp "$orig_git/.git/HEAD" .git/HEAD
# checkout the branch (either the same as HEAD from the original repository, or
# the one that was asked for)
git checkout -f $branch