Fix Mystery Guest

Magic Variable - Change the name of the variable to assign the local variable for partial, rather than `i` use the `index`.

Don't pass a local variable called `i` to a partial.

CHANGELOG

 Please view this file on the master branch, on stable branches it's out of date.
 
 v 8.11.0 (unreleased)
+  - Fix don't pass a local variable called `i` to a partial. !20510 (herminiotorres)
   - Fix the title of the toggle dropdown button. !5515 (herminiotorres)
   - Improve diff performance by eliminating redundant checks for text blobs
   - Convert switch icon into icon font (ClemMakesApps)

app/views/projects/diffs/_diffs.html.haml

@@ -29,5 +29,5 @@
     - next unless blob
     - blob.load_all_data!(diffs.project.repository) unless blob.only_display_raw?
 
-    = render 'projects/diffs/file', i: index, project: diffs.project,
+    = render 'projects/diffs/file', index: index, project: diffs.project,
       diff_file: diff_file, diff_commit: diff_commit, blob: blob

app/views/projects/diffs/_file.html.haml

-.diff-file.file-holder{id: "diff-#{i}", data: diff_file_html_data(project, diff_file)}
+.diff-file.file-holder{id: "diff-#{index}", data: diff_file_html_data(project, diff_file)}
   .file-title{id: "file-path-#{hexdigest(diff_file.file_path)}"}
-    = render "projects/diffs/file_header", diff_file: diff_file, blob: blob, diff_commit: diff_commit, project: project, url: "#diff-#{i}"
+    = render "projects/diffs/file_header", diff_file: diff_file, blob: blob, diff_commit: diff_commit, project: project, url: "#diff-#{index}"
 
     - unless diff_file.submodule?
       .file-actions.hidden-xs