Extract git mixin into its own module

Fixes berkshelf#1208

features/commands/install.feature

@@ -441,7 +441,7 @@ Feature: berks install
       """
       Repository not found.
       """
-      And the exit status should be "GitLocation::GitError"
+      And the exit status should be "GitError"
 
   Scenario: transitive dependencies in metadata
     Given the cookbook store contains a cookbook "fake" "1.0.0" with dependencies:

lib/berkshelf.rb

@@ -22,6 +22,7 @@ module Berkshelf
 
   module Mixin
     autoload :DSLEval, 'berkshelf/mixin/dsl_eval'
+    autoload :Git,     'berkshelf/mixin/git'
     autoload :Logging, 'berkshelf/mixin/logging'
   end
 

lib/berkshelf/errors.rb

@@ -479,4 +479,32 @@ def to_s
       "is the standard error from the command:\n\n#{@output}"
     end
   end
+
+  # Git errors
+  # ------------------------------
+  class GitError < BerkshelfError; status_code(400); end
+
+  class GitNotInstalled < GitError
+    def initialize
+      super 'You need to install Git before you can download ' \
+        'cookbooks from git repositories. For more information, please ' \
+        'see the Git docs: http://git-scm.org. If you have git installed, ' \
+        'please make sure it is in your $PATH and accessible by the user ' \
+        'running this command.'
+    end
+  end
+
+  class GitCommandError < GitError
+    def initialize(command, path, stderr = nil)
+      out =  "Git error: command `git #{command}` failed. If this error "
+      out << "persists, try removing the cache directory at '#{path}'."
+
+      if stderr
+        out << "Output from the command:\n\n"
+        out << stderr
+      end
+
+      super(out)
+    end
+  end
 end

lib/berkshelf/init_generator.rb

@@ -4,6 +4,8 @@
 
 module Berkshelf
   class InitGenerator < BaseGenerator
+    include Mixin::Git
+
     def initialize(*args)
       super(*args)
       if @options[:cookbook_name]
@@ -75,7 +77,7 @@ def generate
 
         unless File.exists?(target.join('.git'))
           inside target do
-            run 'git init', capture: true
+            git 'init'
           end
         end
       end

lib/berkshelf/locations/git.rb

@@ -2,29 +2,7 @@
 
 module Berkshelf
   class GitLocation < BaseLocation
-    class GitError < BerkshelfError; status_code(400); end
-
-    class GitNotInstalled < GitError
-      def initialize
-        super 'You need to install Git before you can download ' \
-          'cookbooks from git repositories. For more information, please ' \
-          'see the Git docs: http://git-scm.org.'
-      end
-    end
-
-    class GitCommandError < GitError
-      def initialize(command, path, stderr = nil)
-        out =  "Git error: command `git #{command}` failed. If this error "
-        out << "persists, try removing the cache directory at '#{path}'."
-
-        if stderr
-          out << "Output from the command:\n\n"
-          out << stderr
-        end
-
-        super(out)
-      end
-    end
+    include Mixin::Git
 
     attr_reader :uri
     attr_reader :branch
@@ -146,29 +124,6 @@ def shortref
 
     private
 
-    # Perform a git command.
-    #
-    # @param [String] command
-    #   the command to run
-    # @param [Boolean] error
-    #   whether to raise error if the command fails
-    #
-    # @raise [String]
-    #   the +$stdout+ from the command
-    def git(command, error = true)
-      unless Berkshelf.which('git') || Berkshelf.which('git.exe')
-        raise GitNotInstalled.new
-      end
-
-      response = Buff::ShellOut.shell_out(%|git #{command}|)
-
-      if error && !response.success?
-        raise GitCommandError.new(command, cache_path, stderr = response.stderr)
-      end
-
-      response.stdout.strip
-    end
-
     # Determine if this git repo has already been downloaded.
     #
     # @return [Boolean]

lib/berkshelf/mixin/git.rb

@@ -0,0 +1,30 @@
+require 'buff/shell_out'
+
+module Berkshelf
+  module Mixin
+    module Git
+      # Perform a git command.
+      #
+      # @param [String] command
+      #   the command to run
+      # @param [Boolean] error
+      #   whether to raise error if the command fails
+      #
+      # @raise [String]
+      #   the +$stdout+ from the command
+      def git(command, error = true)
+        unless Berkshelf.which('git') || Berkshelf.which('git.exe')
+          raise GitNotInstalled.new
+        end
+
+        response = Buff::ShellOut.shell_out(%|git #{command}|)
+
+        if error && !response.success?
+          raise GitCommandError.new(command, cache_path, response.stderr)
+        end
+
+        response.stdout.strip
+      end
+    end
+  end
+end

spec/unit/berkshelf/locations/git_spec.rb

@@ -236,13 +236,13 @@ def rev_parse(instance)
 
       it 'raises an error if Git is not installed' do
         Berkshelf.stub(:which).and_return(false)
-        expect { subject.git('foo') }.to raise_error(GitLocation::GitNotInstalled)
+        expect { subject.git('foo') }.to raise_error(GitNotInstalled)
       end
 
       it 'raises an error if the command fails' do
         shell_out = double('shell_out', success?: false, stderr: nil)
         Buff::ShellOut.stub(:shell_out).and_return(shell_out)
-        expect { subject.git('foo') }.to raise_error(GitLocation::GitCommandError)
+        expect { subject.git('foo') }.to raise_error(GitCommandError)
       end
     end
   end