Clone buildpack(s) locally:
git clone --bare https://github.com/pkgr/heroku-buildpack-ruby.git \
/tmp/heroku-buildpack-ruby.git
Save manifest with a list of buildpacks to use:
cat > manifest <<BUILDPACKS
/tmp/heroku-buildpack-ruby.git#universal,BUILDPACK_NODE_VERSION="0.6.8",CURL_CONNECT_TIMEOUT=30,CURL_TIMEOUT=600
BUILDPACKS
Use it with pkgr:
pkgr package --buildpack-list manifest path/to/app
Or just:
pkgr package --buildpack /tmp/heroku-buildpack-ruby.git#universal --env CURL_TIMEOUT=600 CURL_CONNECT_TIMEOUT=30 path/to/app