Monkey Patch git ruby gem

Previously modulesync would throw an error when a file had a line ending warning
emitted during a diff.  This is common on cross platform modules.  This commit
monkey patches the git ruby gem to handle extra text before the actual diff
contents.  A monkey patch was used as the git ruby gem does not seem to be
actively maintained, and it will some time before this issue is resolved and a
new gem available.

As the monkey_patch can contain code from other parties, which does not conform
to module_sync's rubocopy styles, this file should is ignored explicitly in
rubocops configuration.

.rubocop.yml

@@ -6,6 +6,7 @@ AllCops:
     - 'vendor/**/*'
     - 'tmp/**/*'
     - 'pkg/**/*'
+    - 'lib/monkey_patches.rb'
 
 Style/HashSyntax:
   Enabled: false

lib/modulesync.rb

@@ -7,6 +7,7 @@
 require 'modulesync/renderer'
 require 'modulesync/settings'
 require 'modulesync/util'
+require 'monkey_patches'
 
 module ModuleSync
   include Constants

lib/monkey_patches.rb

@@ -0,0 +1,40 @@
+module Git
+  class Diff
+    # Monkey patch process_full_diff until https://github.com/schacon/ruby-git/issues/326 is resolved
+    def process_full_diff
+      defaults = {
+        :mode => '',
+        :src => '',
+        :dst => '',
+        :type => 'modified'
+      }
+      final = {}
+      current_file = nil
+      full_diff_utf8_encoded = @full_diff.encode("UTF-8", "binary", {
+    :invalid => :replace,
+    :undef => :replace
+  })
+      full_diff_utf8_encoded.split("\n").each do |line|
+        if m = /^diff --git a\/(.*?) b\/(.*?)/.match(line)
+          current_file = m[1]
+          final[current_file] = defaults.merge({:patch => line, :path => current_file})
+        elsif !current_file.nil?
+          if m = /^index (.......)\.\.(.......)( ......)*/.match(line)
+            final[current_file][:src] = m[1]
+            final[current_file][:dst] = m[2]
+            final[current_file][:mode] = m[3].strip if m[3]
+          end
+          if m = /^([[:alpha:]]*?) file mode (......)/.match(line)
+            final[current_file][:type] = m[1]
+            final[current_file][:mode] = m[2]
+          end
+          if m = /^Binary files /.match(line)
+            final[current_file][:binary] = true
+          end
+          final[current_file][:patch] << "\n" + line
+        end
+      end
+      final.map { |e| [e[0], DiffFile.new(@base, e[1])] }
+    end
+  end
+end