Heroku et. al. buildpack that installs packages from a list of packages.

You probably want to compose this with other buildpack(s) using heroku-buildpack-multi (https://github.com/ddollar/heroku-buildpack-multi):

Set your buildpack:

heroku config:set BUILDPACK_URL=https://github.com/ddollar/heroku-buildpack-multi

And add this to your .buildpacks, i.e.:

https://github.com/benalavi/buildpack-packages
https://github.com/heroku/heroku-buildpack-ruby

Then add a file called .packages that is simply a list of packages you want to "install" (really it just unzips them and sets the PATH).

https://s3.amazonaws.com/buildpack-s3cmd/s3cmd-1.0.1.tar.gz
https://s3.amazonaws.com/buildpack-exiftool/exiftool-9.40.tar.gz
https://s3.amazonaws.com/buildpack-zip/zip-3.0.tar.gz

The above would install s3cmd, exiftool, and zip from S3 sources.

The script is very simple: it just downloads and uncompresses the given packages into /app/vendor and then adds /app/vendor/<package name> to PATH.

The packages are expected to be compressed in a specific way: they should uncompress to a folder named the same as the filename, which will be put on PATH. For instance:

tar xvf zip-3.0.tar.gz
./zip-3.0/
./zip-3.0/zip
./zip-3.0/zipsplit
./zip-3.0/zipnote
./zip-3.0/zipcloak

ruby test/buildpack_test.rb

There is also a Vagrantfile which will set up a VM with the build/test environment ready to go:

vagrant up
vagrant ssh
cd /vagrant
ruby test/buildpack_test.rb