Remove duplication, unused methods, and some other style things

app/helpers/diff_helper.rb

@@ -89,6 +89,8 @@ module DiffHelper
   end
 
   def commit_for_diff(diff_file)
+    return diff_file.content_commit if diff_file.content_commit
+    
     if diff_file.deleted_file
       @base_commit || @commit.parent || @commit
     else
@@ -97,7 +99,7 @@ module DiffHelper
   end
 
   def diff_file_html_data(project, diff_file)
-    commit = diff_file.content_commit || commit_for_diff(diff_file)
+    commit = commit_for_diff(diff_file)
     {
       blob_diff_path: namespace_project_blob_diff_path(project.namespace, project,
                                                        tree_join(commit.id, diff_file.file_path))

app/models/concerns/note_on_diff.rb

@@ -33,13 +33,11 @@ module NoteOnDiff
 
   # Returns an array of at most 16 highlighted lines above a diff note
   def truncated_diff_lines
-    prev_match_line = nil
     prev_lines = []
 
     highlighted_diff_lines.each do |line|
       if line.meta?
         prev_lines.clear
-        prev_match_line = line
       else
         prev_lines << line
 

app/models/merge_request.rb

@@ -164,10 +164,6 @@ class MergeRequest < ActiveRecord::Base
     merge_request_diff ? merge_request_diff.first_commit : compare_commits.first
   end
 
-  def last_commit
-    merge_request_diff ? merge_request_diff.last_commit : compare_commits.last
-  end
-
   def diff_size
     merge_request_diff.size
   end
@@ -246,7 +242,7 @@ class MergeRequest < ActiveRecord::Base
   end
 
   def diff_refs
-    return nil unless diff_start_commit || diff_base_commit
+    return unless diff_start_commit || diff_base_commit
 
     Gitlab::Diff::DiffRefs.new(
       base_sha:  diff_base_sha,

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

@@ -23,7 +23,7 @@
 
 .files
   - diff_files.each_with_index do |diff_file, index|
-    - diff_commit = diff_file.content_commit || commit_for_diff(diff_file)
+    - diff_commit = commit_for_diff(diff_file)
     - blob = diff_file.blob(diff_commit)
     - next unless blob
     - blob.load_all_data!(project.repository) unless blob.only_display_raw?

lib/gitlab/diff/file.rb

@@ -21,9 +21,7 @@ module Gitlab
           new_path: new_path,
           old_line: line.old_line,
           new_line: line.new_line,
-          base_sha: diff_refs.base_sha,
-          start_sha: diff_refs.start_sha,
-          head_sha: diff_refs.head_sha
+          diff_refs: diff_refs
         )
       end
 
@@ -121,6 +119,7 @@ module Gitlab
 
       def blob(commit = content_commit)
         return unless commit
+
         repository.blob_at(commit.id, file_path)
       end
     end

lib/gitlab/diff/highlight.rb

@@ -42,10 +42,11 @@ module Gitlab
 
         line_prefix = diff_line.text.match(/\A(.)/) ? $1 : ' '
 
+        rich_line =
           if diff_line.unchanged? || diff_line.added?
-          rich_line = new_lines[diff_line.new_pos - 1]
+            new_lines[diff_line.new_pos - 1]
           elsif diff_line.removed?
-          rich_line = old_lines[diff_line.old_pos - 1]
+            old_lines[diff_line.old_pos - 1]
           end
 
         # Only update text if line is found. This will prevent