[POC][WIP] Add linter to CLI

Allows linting of single branch, or targeted file from that branch.

Currently only running `Rubocop` (since that is all I had available to
test against), but the concept should work for the other linters as
well.

lib/manageiq/style/cli.rb

@@ -17,12 +17,16 @@ def parse_cli_options
           synopsis "\nThe ManageIQ community's style configuration utility."
           version  "v#{ManageIQ::Style::VERSION}\n"
 
-          opt :install, "Install or update the style configurations", :default => false, :required => true
+          opt :format,  "TODO:  How to format the linter output",     :default => "emacs"
+          opt :install, "Install or update the style configurations", :default => false
+          opt :lint,    "Run linters for current changes",            :default => false
+          opt :linters, "Linters to run for current changes",         :default => ["rubocop"]
         end
       end
 
       def run
         install if @opts[:install]
+        lint    if @opts[:lint]
       end
 
       def install
@@ -38,6 +42,20 @@ def install
         update_gem_source
       end
 
+      def lint
+        require 'more_core_extensions/all'
+
+        require 'manageiq/style/git_service/branch'
+        require 'manageiq/style/git_service/diff'
+
+        require 'manageiq/style/linter/base'
+        require 'manageiq/style/linter/haml'
+        require 'manageiq/style/linter/rubocop'
+        require 'manageiq/style/linter/yaml'
+
+        Linter::Rubocop.new(ARGV).run
+      end
+
       private
 
       def check_for_codeclimate_channel