Avoid commit lookup on diff_helper

CHANGELOG

@@ -80,6 +80,7 @@ v 8.11.0 (unreleased)
   - Sensible state specific default sort order for issues and merge requests !5453 (tomb0y)
   - Fix RequestProfiler::Middleware error when code is reloaded in development
   - Catch what warden might throw when profiling requests to re-throw it
+  - Avoid commit lookup on diff_helper passing existing local variable to the helper method
   - Add description to new_issue email and new_merge_request_email in text/plain content type. !5663 (dixpac)
   - Speed up and reduce memory usage of Commit#repo_changes, Repository#expire_avatar_cache and IrkerWorker
   - Add unfold links for Side-by-Side view. !5415 (Tim Masliuchenko)

app/helpers/diff_helper.rb

@@ -109,11 +109,10 @@ module DiffHelper
     end
   end
 
-  def diff_file_html_data(project, diff_file)
-    commit = commit_for_diff(diff_file)
+  def diff_file_html_data(project, diff_file_path, diff_commit_id)
     {
       blob_diff_path: namespace_project_blob_diff_path(project.namespace, project,
-                                                       tree_join(commit.id, diff_file.file_path)),
+                                                       tree_join(diff_commit_id, diff_file_path)),
       view: diff_view
     }
   end

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

-.diff-file.file-holder{id: "diff-#{index}", data: diff_file_html_data(project, diff_file)}
+.diff-file.file-holder{id: "diff-#{index}", data: diff_file_html_data(project, diff_file.file_path, diff_commit.id)}
   .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-#{index}"