Bash script to download folder from GitHub repository

git-dl.sh

#! /bin/bash
if [ -z "$1" ]; then
  echo USAGE: "$0" URL [BRANCH]
  exit
fi

url="$1"
# default to branch master
branch=master
# optional 2nd parameter is branch
if [ -n "$2" ]; then
  branch="$2"
fi

# split url by /
IFS=/ read -r -a parts <<< "$url"
user="${parts[3]}"
repo="${parts[4]}"
# get folder segments starting at 5 to end of array
folders=("${parts[@]:5}")
folder="$(IFS=/; printf '%s' "${folders[*]}")"
# strip off parent folders above specific folder
strip="$((${#parts[@]} - 5))"

# download git archive
# pipe to tar to extract (strip off parent folder)
curl -L "https://github.com/${user}/${repo}/archive/${branch}.tar.gz" \
  | tar -xv --strip-components=${strip} "${repo}-${branch}/${folder}"