Workhorse to serve raw diffs

app/controllers/projects/merge_requests_controller.rb

@@ -57,9 +57,16 @@ class Projects::MergeRequestsController < Projects::ApplicationController
 
     respond_to do |format|
       format.html
-      format.json { render json: @merge_request }
-      format.diff { render text: @merge_request.to_diff }
-      format.patch { render text: @merge_request.to_patch }
+      format.json   { render json: @merge_request }
+      format.patch  { render text: @merge_request.to_patch }
+      format.diff do
+        headers.store(*Gitlab::Workhorse.send_git_diff(@project.repository,
+                                                        @merge_request.diff_base_commit.id,
+                                                        @merge_request.last_commit.id))
+        headers['Content-Disposition'] = 'inline'
+
+        head :ok
+      end
     end
   end
 

app/models/merge_request.rb

@@ -313,13 +313,6 @@ class MergeRequest < ActiveRecord::Base
     )
   end
 
-  # Returns the raw diff for this merge request
-  #
-  # see "git diff"
-  def to_diff
-    target_project.repository.diff_text(diff_base_commit.sha, source_sha)
-  end
-
   # Returns the commit as a series of email patches.
   #
   # see "git format-patch"

features/project/merge_requests.feature

@@ -76,18 +76,6 @@ Feature: Project Merge Requests
     And I submit new merge request "Wiki Feature"
     Then I should see merge request "Wiki Feature"
 
-  Scenario: I download a diff on a public merge request
-    Given public project "Community"
-    And "John Doe" owns public project "Community"
-    And project "Community" has "Bug CO-01" open merge request with diffs inside
-    Given I logout directly
-    And I visit merge request page "Bug CO-01"
-    And I click on "Email Patches"
-    Then I should see a patch diff
-    And I visit merge request page "Bug CO-01"
-    And I click on "Plain Diff"
-    Then I should see a patch diff
-
   @javascript
   Scenario: I comment on a merge request
     Given I visit merge request page "Bug NS-04"

lib/gitlab/workhorse.rb

@@ -30,6 +30,19 @@ module Gitlab
         ]
       end
 
+      def send_git_diff(repository, from, to)
+        params = {
+            'RepoPath'  => repository.path_to_repo,
+            'ShaFrom'   => from,
+            'ShaTo'     => to
+        }
+
+        [
+          SEND_DATA_HEADER,
+          "git-diff:#{encode(params)}"
+        ]
+      end
+
       protected
 
       def encode(hash)

spec/controllers/projects/merge_requests_controller_spec.rb

@@ -84,17 +84,14 @@ describe Projects::MergeRequestsController do
     end
 
     describe "as diff" do
-      include_examples "export merge as", :diff
-      let(:format) { :diff }
-
-      it "should really only be a git diff" do
+      it "triggers workhorse to serve the request" do
         get(:show,
             namespace_id: project.namespace.to_param,
             project_id: project.to_param,
             id: merge_request.iid,
-            format: format)
+            format: :diff)
 
-        expect(response.body).to start_with("diff --git")
+        expect(response.headers['Gitlab-Workhorse-Send-Data']).to start_with("git-diff:")
       end
     end