Some opinions

[shunjikonishi]

Hi,
I've test this buildpack. It works. Good job!

I have some opinions to this buildpack.
Please consider them.

Error of usage

You wrote followings in README.md

$ cat .buildpacks
https://github.com/heroku/heroku-buildpack-toolbelt.git

But its url is not correct. Correct url is

https://github.com/gregburek/heroku-buildpack-toolbelt.git

How to authentication

You use HEROKU_TOOLBELT_API_EMAIL and HEROKU_TOOLBELT_API_PASSWORD to run heroku command.

But I think HEROKU_API_KEY is better than them.
I've verified run it with HEROKU_API_KEY and without HEROKU_TOOLBELT_API_EMAIL and HEROKU_TOOLBELT_API_PASSWORD

In this case, maybe gen-netrc.sh is not neccessary.

Export path to heroku command.

I hope to run command without path to bin.

I've been implemented this feature in other buildpack.

https://github.com/shunjikonishi/heroku-buildpack-ffmpeg/blob/master/bin/compile

You can do it by using .profile.d

Best

Shunji Konishi