Use absolute path to support Cop Exclude param

lib/rubocop/git/commit_file.rb

@@ -6,6 +6,10 @@ def initialize(file, commit)
     @commit = commit
   end
 
+  def absolute_path
+    @file.absolute_path
+  end
+
   def filename
     @file.filename
   end

lib/rubocop/git/pseudo_resource.rb

@@ -1,11 +1,19 @@
 module RuboCop
   module Git
     class PseudoResource
-      attr_reader :filename, :patch
+      attr_reader :patch, :pwd, :file_relative_path
 
-      def initialize(filename)
-        @filename = filename
-        @patch    = ''
+      alias_method :filename, :file_relative_path
+
+      def initialize(file_relative_path, pwd = Dir.pwd)
+        @file_relative_path = file_relative_path
+        @pwd = pwd
+        @patch = ''
+      end
+
+      def absolute_path
+        filename
+        File.join(pwd, filename)
       end
 
       def status

lib/rubocop/git/style_checker.rb

@@ -13,7 +13,7 @@ def initialize(modified_files,
 
   def violations
     file_violations = @modified_files.map do |modified_file|
-      FileViolation.new(modified_file.filename, offenses(modified_file))
+      FileViolation.new(modified_file.absolute_path, offenses(modified_file))
     end
 
     file_violations.select do |file_violation|

lib/rubocop/git/style_guide.rb

@@ -30,19 +30,19 @@ def ignored_file?(file)
   end
 
   def excluded_file?(file)
-    config.file_to_exclude?(file.filename)
+    config.file_to_exclude?(file.absolute_path)
   end
 
   def parse_source(file)
     rubocop_version = Gem::Version.new(RuboCop::Version::STRING)
     if rubocop_version < Gem::Version.new('0.36.0')
-      RuboCop::ProcessedSource.new(file.content, file.filename)
+      RuboCop::ProcessedSource.new(file.content, file.absolute_path)
     elsif rubocop_version < Gem::Version.new('0.41.0')
       RuboCop::ProcessedSource.new(file.content,
-                                   target_ruby_version, file.filename)
+                                   target_ruby_version, file.absolute_path)
     else
       RuboCop::ProcessedSource.new(file.content,
-                                   config.target_ruby_version, file.filename)
+                                   config.target_ruby_version, file.absolute_path)
     end
   end