Auto merge of #4063 - A5308Y:master, r=segiddins

Extracting a new "GemInstaller" from installer.rb

My goal was to reveal the main part of install_gem_from_spec. From my
perspective the main part is:
1. Install
2. Generate stubs
3. Print message to the user
(4. handle exceptions)

While working on it I found that Bundler::Installer's run method and
instance variables weren't used when installing gems with
install_gem_from_spec. The installer was (and still is) only used to
generate executable stubs.
So I inserted the new GemInstaller in ParallelInstaller; passing the
instantiated Bundler::Installer to the GemInstaller only to generate
the executable stubs.

Based on this I would continue by extracting two BinstubGenerator
classes and removing GemInstaller's dependency on Bundler::Installer,
possibly allowing for a more concise way to generate binstubs in other
parts of bundler.

I was a bit intimidated by the amount of installers and weary to add
another one to this contested namespace. So I checked in with
@indirect who approved of the general direction of the refactoring and
suggested to rename the old GemInstaller to RubyGemsGemInstaller.

0 files changed, 0 insertions, 0 deletions