Show a notice for diffs that are too large

This builds on the changes introduced in
https://gitlab.com/gitlab-org/gitlab_git/merge_requests/72 and results
in merge requests with large diffs (e.g. due to them containing minified
CSS) loading much faster.

Gemfile

@@ -51,7 +51,7 @@ gem "browser", '~> 1.0.0'
 # Extracting information from a git repository
 # Provide access to Gitlab::Git library
-gem "gitlab_git", '~> 9.0'
+gem "gitlab_git", '~> 10.0'
 # LDAP Auth
 # GitLab fork with several improvements to original library. For full list of changes

Gemfile.lock

@@ -359,11 +359,11 @@ GEM
       posix-spawn (~> 0.3)
     gitlab_emoji (0.3.1)
       gemojione (~> 2.2, >= 2.2.1)
-    gitlab_git (9.0.3)
+    gitlab_git (10.0.0)
       activesupport (~> 4.0)
       charlock_holmes (~> 0.7.3)
       github-linguist (~> 4.7.0)
-      rugged (~> 0.24.0b13)
+      rugged (~> 0.24.0)
     gitlab_meta (7.0)
     gitlab_omniauth-ldap (1.2.1)
       net-ldap (~> 0.9)
@@ -942,7 +942,7 @@ DEPENDENCIES
   github-markup (~> 1.3.1)
   gitlab-flowdock-git-hook (~> 1.0.1)
   gitlab_emoji (~> 0.3.0)
-  gitlab_git (~> 9.0)
+  gitlab_git (~> 10.0)
   gitlab_meta (= 7.0)
   gitlab_omniauth-ldap (~> 1.2.1)
   gollum-lib (~> 4.1.0)

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

@@ -42,13 +42,17 @@
   .diff-content.diff-wrap-lines
     -# Skipp all non non-supported blobs
     - return unless blob.respond_to?('text?')
-    - if 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.image?
-      - old_file = project.repository.prev_blob_for_diff(diff_commit, diff_file)
-      = render "projects/diffs/image", diff_file: diff_file, old_file: old_file, file: blob, index: i
+    - if diff_file.too_large?
+      .nothing-here-block
+        This diff could not be displayed because it is too large.
     - else
-      .nothing-here-block No preview for this file type
+      - if 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.image?
+        - old_file = project.repository.prev_blob_for_diff(diff_commit, diff_file)
+        = render "projects/diffs/image", diff_file: diff_file, old_file: old_file, file: blob, index: i
+      - else
+        .nothing-here-block No preview for this file type

lib/gitlab/diff/file.rb

@@ -24,6 +24,10 @@ module Gitlab
         @lines ||= parser.parse(raw_diff.each_line).to_a
       end
+      def too_large?
+        diff.too_large?
+      end
+
       def highlighted_diff_lines
         Gitlab::Diff::Highlight.new(self).highlight
       end

spec/lib/gitlab/diff/file_spec.rb

@@ -18,4 +18,18 @@ describe Gitlab::Diff::File, lib: true do
   describe :mode_changed? do
     it { expect(diff_file.mode_changed?).to be_falsey }
   end
+
+  describe '#too_large?' do
+    it 'returns true for a file that is too large' do
+      expect(diff).to receive(:too_large?).and_return(true)
+
+      expect(diff_file.too_large?).to eq(true)
+    end
+
+    it 'returns false for a file that is small enough' do
+      expect(diff).to receive(:too_large?).and_return(false)
+
+      expect(diff_file.too_large?).to eq(false)
+    end
+  end
 end