Fix Compare view for renames on JRuby (#1682)

test/test_compare.rb

@@ -13,6 +13,18 @@ context "Precious::Views::Compare" do
     # Precious::App.set(:gollum_path, @path)
     @wiki = Gollum::Wiki.new(@path)
   end
+  
+  test 'rename diff' do
+    # JGit returns differenly formatted diffs for rename commits. Support both kinds of diff.
+    jgit_diff = "diff --git a/Foo.md b/Bar.md\nsimilarity index 100%\nrename from Foo.md\nrename to Bar.md"
+    rugged_diff = "diff --git a/Bar.md b/Bar.md\nnew file mode 100644\nindex 0000000..e69de29\n--- /dev/null\n+++ b/Bar.md\n"
+  
+    [jgit_diff, rugged_diff].each do |diff|
+      view = Precious::Views::Compare.new
+      view.instance_variable_set(:@diff, diff)
+      assert_equal [], view.lines
+    end
+  end
 
   test 'file addition diff' do
     view = Precious::Views::Compare.new