Fork repo locally

forkrepo.sh

#!/bin/sh

if [ $# -ne 2 ]; then
	echo "usage: ${0##*/} <source> <target>"
	echo "	clone 'source' to 'target' sharing objects"
	exit 1
fi

src=$1
trg=$2

if ! [ -d "$src/.git/objects" ]; then
	echo "$src is not a git repository"
	exit 1
fi

branch=$(git -C "$src" branch --show-current)
remote=$(git -C "$src" config "branch.$branch.remote")
url=$(git -C "$src" config "remote.$remote.url")
git init -b "$branch" "$trg"
git -C "$trg" remote add "$remote" "$url"
realpath --relative-to="$trg/.git/objects" "$src/.git/objects" >"$trg/.git/objects/info/alternates"
git -C "$trg" fetch
git -C "$trg" checkout "$branch"