Bypass recursive RubyGems require

[aycabta]

I fixed a bug that I reported for Rake test problem.

First, Bundler::Plugin uses cascading autoload for Bundler::Plugin::API and Bundler::Plugin::API::Source.

Secondly, Bundler uses monkey patch for RubyGems loading logic, thus Gem::Specification#full_gem_path is overridden.

Next, if a module is loaded by require in RubyGems with Bundler's monkey patch, the Gem::Specification#full_gem_path that uses Bundler::Plugin::API::Source is called in it. But bundler/plugin/api/source uses require before Bundler::Plugin::API::Source is defined. RubyGems loading logic runs again by the require. Bundler::Plugin::API::Source is not defined yet. Gem::Specification#full_gem_path is called again, and it uses Bundler::Plugin::API::Source. The autoload is skipped after 2nd call. So exception is occurred.

NameError: uninitialized constant Bundler::Plugin::API::Source

This Pull Request bypasses the recursive RubyGems require.

[segiddins]

If this fixes a bug, could you see if it's possible to add test coverage? Thanks!

[aycabta]

#4981 is better then this Pull Request for this problem.