Merge branch 'faster-diff-rendering' into 'master'

Faster diff rendering

1. Dont render link in separate template but use helper instead
2. Don't build new object but just reuse variables

New note for diff is rendered per each diff line. Such simple improvements gives us 20..100% better performance depends on diff size

app/helpers/notes_helper.rb

@@ -42,4 +42,23 @@ module NotesHelper
       project_id: noteable.project.id,
     }.to_json
   end
+
+  def link_to_new_diff_note(line_code)
+    discussion_id = Note.build_discussion_id(
+      @comments_target[:noteable_type],
+      @comments_target[:noteable_id] || @comments_target[:commit_id],
+      line_code
+    )
+
+    data = {
+      noteable_type: @comments_target[:noteable_type],
+      noteable_id:   @comments_target[:noteable_id],
+      commit_id:     @comments_target[:commit_id],
+      line_code:     line_code,
+      discussion_id: discussion_id
+    }
+
+    link_to "", "javascript:;", class: "add-diff-note js-add-diff-note-button",
+      data: data, title: "Add a comment to this line"
+  end
 end

app/models/note.rb

@@ -122,11 +122,15 @@ class Note < ActiveRecord::Base
 
       discussions
     end
-  end
 
-  # Determine whether or not a cross-reference note already exists.
-  def self.cross_reference_exists?(noteable, mentioner)
-    where(noteable_id: noteable.id, system: true, note: "_mentioned in #{mentioner.gfm_reference}_").any?
+    def build_discussion_id(type, id, line_code)
+      [:discussion, type.try(:underscore), id, line_code].join("-").to_sym
+    end
+
+    # Determine whether or not a cross-reference note already exists.
+    def cross_reference_exists?(noteable, mentioner)
+      where(noteable_id: noteable.id, system: true, note: "_mentioned in #{mentioner.gfm_reference}_").any?
+    end
   end
 
   def commit_author
@@ -194,7 +198,7 @@ class Note < ActiveRecord::Base
   end
 
   def discussion_id
-    @discussion_id ||= [:discussion, noteable_type.try(:underscore), noteable_id || commit_id, line_code].join("-").to_sym
+    @discussion_id ||= Note.build_discussion_id(noteable_type, noteable_id || commit_id, line_code)
   end
 
   # Returns true if this is a downvote note,

app/views/projects/commits/_text_file.html.haml

@@ -13,7 +13,7 @@
         %td.old_line
           = link_to raw(type == "new" ? " " : line_old), "##{line_code}", id: line_code
           - if @comments_allowed
-            = render "projects/notes/diff_note_link", line_code: line_code
+            = link_to_new_diff_note(line_code)
         %td.new_line= link_to raw(type == "old" ? " " : line_new) , "##{line_code}", id: line_code
         %td.line_content{class: "noteable_line #{type} #{line_code}", "line_code" => line_code}= raw diff_line_content(line)