1 files changed, 17 insertions, 17 deletions

diff --git a/app/controllers/projects/merge_requests_controller.rb b/app/controllers/projects/merge_requests_controller.rb
index dd86b940a08..df1943dd9bb 100644
--- a/app/controllers/projects/merge_requests_controller.rb
+++ b/app/controllers/projects/merge_requests_controller.rb
@@ -58,14 +58,17 @@ class Projects::MergeRequestsController < Projects::ApplicationController
 
     respond_to do |format|
       format.html
-      format.json   { render json: @merge_request }
+      
+      format.json do
+        render json: @merge_request
+      end
+
       format.patch  do
-        headers.store(*Gitlab::Workhorse.send_git_patch(@project.repository,
-                                                        @merge_request.diff_base_commit.id,
-                                                        @merge_request.last_commit.id))
-        headers['Content-Disposition'] = 'inline'
-        head :ok
+        return render_404 unless @merge_request.diff_refs
+
+        send_git_patch @project.repository, @merge_request.diff_refs
       end
+
       format.diff do
         return render_404 unless @merge_request.diff_refs
 
@@ -77,18 +80,15 @@ class Projects::MergeRequestsController < Projects::ApplicationController
   def diffs
     apply_diff_view_cookie!
 
-    @commit = @merge_request.last_commit
-    @base_commit = @merge_request.diff_base_commit
-
-    # MRs created before 8.4 don't have a diff_base_commit,
-    # but we need it for the "View file @ ..." link by deleted files
-    @base_commit ||= @merge_request.first_commit.parent || @merge_request.first_commit
+    @commit = @merge_request.diff_head_commit
+    @base_commit = @merge_request.diff_base_commit || @merge_request.likely_diff_base_commit
 
     @comments_target = {
       noteable_type: 'MergeRequest',
       noteable_id: @merge_request.id
     }
 
+    @use_legacy_diff_notes = !@merge_request.support_new_diff_notes?
     @grouped_diff_notes = @merge_request.notes.grouped_diff_notes
 
     Banzai::NoteRenderer.render(
@@ -134,7 +134,7 @@ class Projects::MergeRequestsController < Projects::ApplicationController
     @target_project = merge_request.target_project
     @source_project = merge_request.source_project
     @commits = @merge_request.compare_commits.reverse
-    @commit = @merge_request.last_commit
+    @commit = @merge_request.diff_head_commit
     @base_commit = @merge_request.diff_base_commit
     @diffs = @merge_request.compare.diffs(diff_options) if @merge_request.compare
     @diff_notes_disabled = true
@@ -212,7 +212,7 @@ class Projects::MergeRequestsController < Projects::ApplicationController
       return
     end
 
-    if params[:sha] != @merge_request.source_sha
+    if params[:sha] != @merge_request.diff_head_sha
       @status = :sha_mismatch
       return
     end
@@ -274,16 +274,16 @@ class Projects::MergeRequestsController < Projects::ApplicationController
       status ||= "preparing"
     else
       ci_service = @merge_request.source_project.ci_service
-      status = ci_service.commit_status(merge_request.last_commit.sha, merge_request.source_branch) if ci_service
+      status = ci_service.commit_status(merge_request.diff_head_sha, merge_request.source_branch) if ci_service
 
       if ci_service.respond_to?(:commit_coverage)
-        coverage = ci_service.commit_coverage(merge_request.last_commit.sha, merge_request.source_branch)
+        coverage = ci_service.commit_coverage(merge_request.diff_head_sha, merge_request.source_branch)
       end
     end
 
     response = {
       title: merge_request.title,
-      sha: merge_request.last_commit_short_sha,
+      sha: merge_request.diff_head_commit.short_id,
       status: status,
       coverage: coverage
     }