Ignore invalid encoding when parsing attributes

This prevents us from raising a hard error when parsing Git attribute
files that are encoded using an invalid/unsupported encoding. This in
turn means a GitLab user won't be presented with an HTTP 500 error.

Fixes #28

CHANGELOG

+v 10.6.10
+  - Ignore invalid encodings when parsing Git attribute files
+
 v 10.6.9
   - Optimize diff creation from Rugged::Patch

lib/gitlab_git/attributes.rb

@@ -99,6 +99,8 @@ module Gitlab
         File.open(full_path, 'r') do |handle|
           handle.each_line do |line|
+            break unless line.valid_encoding?
+
             yield line.strip
           end
         end

spec/attributes_spec.rb

@@ -139,5 +139,12 @@ describe Gitlab::Git::Attributes do
       expect { |b| subject.each_line(&b) }.not_to yield_control
     end
+
+    it 'does not yield when the attributes file has an unsupported encoding' do
+      path = File.expand_path(File.join(SUPPORT_PATH, 'with-invalid-git-attributes.git'))
+      attrs = described_class.new(path)
+
+      expect { |b| attrs.each_line(&b) }.not_to yield_control
+    end
   end
 end

spec/support/seed_helper.rb

@@ -13,6 +13,7 @@ module SeedHelper
     create_mutable_seeds
     create_broken_seeds
     create_git_attributes
+    create_invalid_git_attributes
   end
   def create_bare_seeds
@@ -75,6 +76,18 @@ bla/bla.txt
     end
   end
+  def create_invalid_git_attributes
+    dir = File.join(SUPPORT_PATH, 'with-invalid-git-attributes.git', 'info')
+
+    FileUtils.mkdir_p(dir)
+
+    enc = Encoding::UTF_16
+
+    File.open(File.join(dir, 'attributes'), 'w', encoding: enc) do |handle|
+      handle.write('# hello'.encode(enc))
+    end
+  end
+
   # Prevent developer git configurations from being persisted to test
   # repositories
   def git_env