Style diff and blob file headers the same way

app/assets/stylesheets/framework/files.scss

@@ -50,7 +50,7 @@
     }
     a:not(.btn) {
-      color: $gl-dark-link-color;
+      color: $gl-text-color;
     }
     .left-options {

app/helpers/application_helper.rb

@@ -306,4 +306,15 @@ module ApplicationHelper
   def truncate_first_line(message, length = 50)
     truncate(message.each_line.first.chomp, length: length) if message
   end
+
+  # While similarly named to Rails's `link_to_if`, this method behaves quite differently.
+  # If `condition` is truthy, a link will be returned with the result of the block
+  # as its body. If `condition` is falsy, only the result of the block will be returned.
+  def conditional_link_to(condition, options, html_options = {}, &block)
+    if condition
+      link_to options, html_options, &block
+    else
+      capture(&block)
+    end
+  end
 end

app/helpers/notes_helper.rb

@@ -79,4 +79,14 @@ module NotesHelper
     full_key = { project: note.project, user_id: note.author_id }
     @max_access_by_user_id[full_key]
   end
+
+  def diff_note_path(note)
+    return unless note.diff_note?
+
+    if note.for_merge_request? && note.active?
+      diffs_namespace_project_merge_request_path(note.project.namespace, note.project, note.noteable, anchor: note.line_code)
+    elsif note.for_commit?
+      namespace_project_commit_path(note.project.namespace, note.project, note.noteable, anchor: note.line_code)
+    end
+  end
 end

app/views/notify/note_merge_request_email.html.haml

-- if @note.legacy_diff_note?
+- if @note.diff_note?
   %p.details
     New comment on diff for
-    = link_to @note.diff_file_path, @target_url
+    = link_to @note.diff_file.file_path, @target_url
     \:
 = render 'note_message'

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

 .diff-file.file-holder{id: "diff-#{i}", data: diff_file_html_data(project, diff_file)}
   .file-title{id: "file-path-#{hexdigest(diff_file.file_path)}"}
-    - if diff_file.diff.submodule?
-      %span
-        = icon('archive fw')
-        %span
-          = submodule_link(blob, @commit.id, project.repository)
-    - else
-      = blob_icon blob.mode, blob.name
-
-      = link_to "#diff-#{i}" do
-        - if diff_file.renamed_file
-          - old_path, new_path = mark_inline_diffs(diff_file.old_path, diff_file.new_path)
-          = old_path
-          →
-          = new_path
-        - else
-          %span
-            = diff_file.new_path
-          - if diff_file.deleted_file
-            deleted
-
-      - if diff_file.mode_changed?
-        %small
-          = "#{diff_file.diff.a_mode} → #{diff_file.diff.b_mode}"
+    = render "projects/diffs/file_header", diff_file: diff_file, blob: blob, diff_commit: diff_commit, project: project, url: "#diff-#{i}"
+    - unless diff_file.submodule?
       .file-actions.hidden-xs
         - if blob_text_viewable?(blob)
           = link_to '#', class: 'js-toggle-diff-comments btn active has-tooltip btn-file-option', title: "Toggle comments for this file" do
@@ -42,15 +21,21 @@
     - return unless blob.respond_to?(:text?)
     - if diff_file.too_large?
       .nothing-here-block This diff could not be displayed because it is too large.
-    - elsif blob_text_viewable?(blob) && !project.repository.diffable?(blob)
-      .nothing-here-block This diff was suppressed by a .gitattributes entry.
-    - elsif blob_text_viewable?(blob)
-      - if diff_view == 'parallel'
-        = render "projects/diffs/parallel_view", diff_file: diff_file, project: project, blob: blob, index: i
-      - else
-        = render "projects/diffs/text_file", diff_file: diff_file, index: i
     - elsif blob.only_display_raw?
       .nothing-here-block This file is too large to display.
+    - elsif blob_text_viewable?(blob)
+      - if !project.repository.diffable?(blob)
+        .nothing-here-block This diff was suppressed by a .gitattributes entry.
+      - elsif diff_file.diff_lines.length > 0
+        - if diff_view == 'parallel'
+          = render "projects/diffs/parallel_view", diff_file: diff_file, project: project, blob: blob, index: i
+        - else
+          = render "projects/diffs/text_file", diff_file: diff_file, index: i
+      - else
+        - if diff_file.mode_changed?
+          .nothing-here-block File mode changed
+        - elsif diff_file.renamed_file
+          .nothing-here-block File moved
     - elsif blob.image?
       - old_blob = diff_file.old_blob(diff_commit)
       = render "projects/diffs/image", diff_file: diff_file, old_file: old_blob, file: blob, index: i

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

+- if defined?(blob) && blob && diff_file.submodule?
+  %span
+    = icon('archive fw')
+    %span
+      = submodule_link(blob, diff_commit.id, project.repository)
+- else
+  = conditional_link_to url.present?, url do
+    = blob_icon diff_file.b_mode, diff_file.file_path
+
+    - if diff_file.renamed_file
+      - old_path, new_path = mark_inline_diffs(diff_file.old_path, diff_file.new_path)
+      %strong
+        = old_path
+      →
+      %strong
+        = new_path
+    - else
+      %strong
+        = diff_file.new_path
+      - if diff_file.deleted_file
+        deleted
+
+  - if diff_file.mode_changed?
+    %small
+      = "#{diff_file.a_mode} → #{diff_file.b_mode}"

app/views/projects/notes/discussions/_diff_with_notes.html.haml

 - note = discussion_notes.first
-- diff = note.diff
-- return unless diff
-.diff-file
-  .diff-header
-    %span
-      - if diff.deleted_file
-        = diff.old_path
-      - else
-        = diff.new_path
-        - if diff.a_mode && diff.b_mode && diff.a_mode != diff.b_mode
-          %span.file-mode= "#{diff.a_mode} → #{diff.b_mode}"
+- diff_file = note.diff_file
+- return unless diff_file
+
+- blob = note.blob
+
+.diff-file.file-holder
+  .file-title
+    = render "projects/diffs/file_header", diff_file: diff_file, blob: blob, diff_commit: diff_file.content_commit, project: note.project, url: diff_note_path(note)
   .diff-content.code.js-syntax-highlight
     %table
       - note.truncated_diff_lines.each do |line|

lib/gitlab/diff/file.rb

@@ -4,7 +4,8 @@ module Gitlab
       attr_reader :diff, :repository, :diff_refs
       delegate :new_file, :deleted_file, :renamed_file,
-        :old_path, :new_path, to: :diff, prefix: false
+        :old_path, :new_path, :a_mode, :b_mode,
+        :submodule?, :too_large?, to: :diff, prefix: false
       def initialize(diff, repository:, diff_refs: nil)
         @diff = diff
@@ -40,11 +41,7 @@ module Gitlab
       end
       def mode_changed?
-        !!(diff.a_mode && diff.b_mode && diff.a_mode != diff.b_mode)
-      end
-
-      def parser
-        Gitlab::Diff::Parser.new
+        a_mode && b_mode && a_mode != b_mode
       end
       def raw_diff
@@ -56,13 +53,11 @@ module Gitlab
       end
       def prev_line(index)
-        if index > 0
-          diff_lines[index - 1]
-        end
+        diff_lines[index - 1] if index > 0
       end
       def file_path
-        new_path.presence || old_path.presence
+        new_path.presence || old_path
       end
       def added_lines