Use gitlab_git 5.4.0 without BROKEN_DIFF constant

Gemfile

@@ -29,7 +29,7 @@ gem 'omniauth-github'
 
 # Extracting information from a git repository
 # Provide access to Gitlab::Git library
-gem "gitlab_git", '~> 5.3.0'
+gem "gitlab_git", '~> 5.4.0'
 
 # Ruby/Rack Git Smart-HTTP Server Handler
 gem 'gitlab-grack', '~> 2.0.0.pre', require: 'grack'

Gemfile.lock

@@ -177,7 +177,7 @@ GEM
       charlock_holmes (~> 0.6.6)
       escape_utils (~> 0.2.4)
       mime-types (~> 1.19)
-    gitlab_git (5.3.0)
+    gitlab_git (5.4.0)
       activesupport (~> 4.0.0)
       charlock_holmes (~> 0.6.9)
       gitlab-grit (~> 2.6.1)
@@ -579,7 +579,7 @@ DEPENDENCIES
   gitlab-gollum-lib (~> 1.1.0)
   gitlab-grack (~> 2.0.0.pre)
   gitlab-linguist (~> 3.0.0)
-  gitlab_git (~> 5.3.0)
+  gitlab_git (~> 5.4.0)
   gitlab_meta (= 6.0)
   gitlab_omniauth-ldap (= 1.0.4)
   gon (~> 5.0.0)

app/controllers/projects/compare_controller.rb

@@ -15,11 +15,7 @@ class Projects::CompareController < Projects::ApplicationController
     @diffs         = compare.diffs
     @refs_are_same = compare.same
     @line_notes    = []
-
-    if @diffs == [Gitlab::Git::Diff::BROKEN_DIFF]
-      @diffs = []
-      @timeout = true
-    end
+    @timeout       = compare.timeout
 
     diff_line_count = Commit::diff_line_count(@diffs)
     @suppress_diff = Commit::diff_suppress?(@diffs, diff_line_count) && !params[:force_show_diff]

app/models/merge_request_diff.rb

@@ -148,13 +148,11 @@ class MergeRequestDiff < ActiveRecord::Base
               Gitlab::Git::Diff.between(repository, source_branch, target_branch)
             end
 
-    if diffs == broken_diffs
-      self.state = :timeout
-      diffs = []
-    end
-
     diffs ||= []
     diffs
+  rescue Gitlab::Git::Diff::TimeoutError => ex
+    self.state = :timeout
+    diffs = []
   end
 
   def repository