Persist truncated note diffs on a new table45190-create-notes-diff-files

We request Gitaly in a N+1 manner to build discussion diffs. Once the diffs are from different revisions, it's hard to make a single request to the service in order to build the whole response.
With this change we solve this problem and simplify a lot fetching this piece of info.

2 files changed, 55 insertions, 0 deletions

diff --git a/spec/lib/gitlab/diff/file_spec.rb b/spec/lib/gitlab/diff/file_spec.rb
index 0c2e18c268a..0588fe935c3 100644
--- a/spec/lib/gitlab/diff/file_spec.rb
+++ b/spec/lib/gitlab/diff/file_spec.rb
@@ -468,4 +468,58 @@ describe Gitlab::Diff::File do
       end
     end
   end
+
+  describe '#diff_hunk' do
+    let(:raw_diff) do
+      <<EOS
+@@ -6,12 +6,18 @@ module Popen
+
+   def popen(cmd, path=nil)
+     unless cmd.is_a?(Array)
+-      raise "System commands must be given as an array of strings"
++      raise RuntimeError, "System commands must be given as an array of strings"
+     end
+
+     path ||= Dir.pwd
+-    vars = { "PWD" => path }
+-    options = { chdir: path }
++
++    vars = {
++      "PWD" => path
++    }
++
++    options = {
++      chdir: path
++    }
+
+     unless File.directory?(path)
+       FileUtils.mkdir_p(path)
+@@ -19,6 +25,7 @@ module Popen
+
+     @cmd_output = ""
+     @cmd_status = 0
++
+     Open3.popen3(vars, *cmd, options) do |stdin, stdout, stderr, wait_thr|
+       @cmd_output << stdout.read
+       @cmd_output << stderr.read
+EOS
+    end
+
+    it 'returns raw diff up to given line index' do
+      allow(diff_file).to receive(:raw_diff) { raw_diff }
+      diff_line = instance_double(Gitlab::Diff::Line, index: 5)
+
+      diff_hunk = <<EOS
+@@ -6,12 +6,18 @@ module Popen
+
+   def popen(cmd, path=nil)
+     unless cmd.is_a?(Array)
+-      raise "System commands must be given as an array of strings"
++      raise RuntimeError, "System commands must be given as an array of strings"
+     end
+EOS
+
+      expect(diff_file.diff_hunk(diff_line)).to eq(diff_hunk)
+    end
+  end
 end
diff --git a/spec/lib/gitlab/import_export/all_models.yml b/spec/lib/gitlab/import_export/all_models.yml
index 8b46b04b8b5..fb5fd300dbb 100644
--- a/spec/lib/gitlab/import_export/all_models.yml
+++ b/spec/lib/gitlab/import_export/all_models.yml
@@ -35,6 +35,7 @@ notes:
 - todos
 - events
 - system_note_metadata
+- note_diff_file
 label_links:
 - target
 - label