make heroku gem not installable in bundler

[kr]

@geemus mentioned that having the heroku gem in your bundle can cause
problematic interactions with toolbelt. Is there a way to make it not possible
to put the heroku gem in a bundle? Now that we have heroku.rb, there should
be little reason for anyone to actually want the heroku gem in a bundle.

@hone is this possible? What's the best way?

[danp]

One reason to have the heroku gem in a bundle is it provides easy access to a ready-to-go Heroku::API instance by way of Heroku::Auth.api. I have been meaning to open an issue somewhere to see about splitting that out but I currently have the heroku gem in a bundle for this reason.

[kr]

@dpiddy is this something that could be provided by https://github.com/heroku/heroku.rb?

[danp]

Opened heroku/heroku.rb#23 to discuss the possibility there.

[hone]

@kr no, I don't think so. It's a proper gem and there isn't a way to special case it. The gems shouldn't be depending on it if you don't want it in the bundle? I guess I'm not totally understanding the use case here.

[geemus]

@hone - I think the thing we want to stop is people putting heroku in their rails app bundle because they think they have to or need to (when they would be better off using a globally installed version). I think deprecations will help with some of this, but we need the gem version for some platforms (though bundling is still often not needed). In particular people doing this + automagic bundle exec stuff has caused several issues.

[ddollar]

@geemus The bin loader for the gem should be able to detect that the toolbelt is installed at the system level. Once detected you can do two things:

1. Warn the user that they're doing something wrong (don't bundle heroku, etc)
2. Go ahead and execute their command, but use the system toolbelt

Should be able to re-use the bits about how the client defers to ~/.heroku/client when detected to defer up to the system toolbelt.

[geemus]

Working on figuring out the correct defer patterns, but in the mean time I believe I just fixed the thing causing the gem/toolbelt conflicts here: cbdbcfb