Add a "patch" MIME type, and render it like a normal view in Commit#show

app/controllers/commit_controller.rb

@@ -15,19 +15,22 @@ class CommitController < ApplicationController
     result = CommitLoad.new(project, current_user, params).execute
 
     @commit = result[:commit]
+    git_not_found! unless @commit
 
-    if @commit
     @suppress_diff    = result[:suppress_diff]
     @note             = result[:note]
     @line_notes       = result[:line_notes]
     @notes_count      = result[:notes_count]
     @comments_allowed = true
-    else
-      return git_not_found!
-    end
 
+    respond_to do |format|
+      format.html do
         if result[:status] == :huge_commit
           render "huge_commit" and return
         end
       end
+
+      format.patch
+    end
+  end
 end

app/controllers/commits_controller.rb

@@ -25,15 +25,4 @@ class CommitsController < ApplicationController
       format.atom { render layout: false }
     end
   end
-
-  def patch
-    @commit = project.commit(params[:id])
-
-    send_data(
-      @commit.to_patch,
-      type: "text/plain",
-      disposition: 'attachment',
-      filename: "#{@commit.id}.patch"
-    )
-  end
 end

app/views/commit/show.patch.erb

+<%= @commit.to_patch %>

config/initializers/mime_types.rb

@@ -3,3 +3,5 @@
 # Add new mime types for use in respond_to blocks:
 # Mime::Type.register "text/richtext", :rtf
 # Mime::Type.register_alias "text/html", :iphone
+
+Mime::Type.register_alias 'text/plain', :patch