Fix GitHub Importer outdated diff notes not showing

  - Update diff notes coming from GitHub to include
    original_commit_id instead of commit_id as well
    as add discussion_id to fix display of these
    notes in the UI

Changelog: fixed

lib/gitlab/github_import/importer/diff_note_importer.rb

@@ -24,13 +24,14 @@ module Gitlab
           note_body = MarkdownText.format(note.note, note.author, author_found)
 
           attributes = {
+            discussion_id: Discussion.discussion_id(note),
             noteable_type: 'MergeRequest',
             noteable_id: mr_id,
             project_id: project.id,
             author_id: author_id,
             note: note_body,
             system: false,
-            commit_id: note.commit_id,
+            commit_id: note.original_commit_id,
             line_code: note.line_code,
             type: 'LegacyDiffNote',
             created_at: note.created_at,

lib/gitlab/github_import/representation/diff_note.rb

@@ -11,7 +11,7 @@ module Gitlab
 
         expose_attribute :noteable_type, :noteable_id, :commit_id, :file_path,
                          :diff_hunk, :author, :note, :created_at, :updated_at,
-                         :github_id
+                         :github_id, :original_commit_id
 
         NOTEABLE_ID_REGEX = %r{/pull/(?<iid>\d+)}i.freeze
 
@@ -34,6 +34,7 @@ module Gitlab
             noteable_id: matches[:iid].to_i,
             file_path: note.path,
             commit_id: note.commit_id,
+            original_commit_id: note.original_commit_id,
             diff_hunk: note.diff_hunk,
             author: user,
             note: note.body,

spec/lib/gitlab/github_import/importer/diff_note_importer_spec.rb

@@ -20,6 +20,7 @@ RSpec.describe Gitlab::GithubImport::Importer::DiffNoteImporter do
       noteable_type: 'MergeRequest',
       noteable_id: 1,
       commit_id: '123abc',
+      original_commit_id: 'original123abc',
       file_path: 'README.md',
       diff_hunk: hunk,
       author: Gitlab::GithubImport::Representation::User
@@ -64,13 +65,14 @@ RSpec.describe Gitlab::GithubImport::Importer::DiffNoteImporter do
             LegacyDiffNote.table_name,
             [
               {
+                discussion_id: anything,
                 noteable_type: 'MergeRequest',
                 noteable_id: merge_request.id,
                 project_id: project.id,
                 author_id: user.id,
                 note: 'Hello',
                 system: false,
-                commit_id: '123abc',
+                commit_id: 'original123abc',
                 line_code: note.line_code,
                 type: 'LegacyDiffNote',
                 created_at: created_at,
@@ -95,13 +97,14 @@ RSpec.describe Gitlab::GithubImport::Importer::DiffNoteImporter do
             LegacyDiffNote.table_name,
             [
               {
+                discussion_id: anything,
                 noteable_type: 'MergeRequest',
                 noteable_id: merge_request.id,
                 project_id: project.id,
                 author_id: project.creator_id,
                 note: "*Created by: #{user.username}*\n\nHello",
                 system: false,
-                commit_id: '123abc',
+                commit_id: 'original123abc',
                 line_code: note.line_code,
                 type: 'LegacyDiffNote',
                 created_at: created_at,

spec/lib/gitlab/github_import/importer/diff_notes_importer_spec.rb

@@ -12,6 +12,7 @@ RSpec.describe Gitlab::GithubImport::Importer::DiffNotesImporter do
       html_url: 'https://github.com/foo/bar/pull/42',
       path: 'README.md',
       commit_id: '123abc',
+      original_commit_id: 'original123abc',
       diff_hunk: "@@ -1 +1 @@\n-Hello\n+Hello world",
       user: double(:user, id: 4, login: 'alice'),
       body: 'Hello world',

spec/lib/gitlab/github_import/representation/diff_note_spec.rb

@@ -67,6 +67,7 @@ RSpec.describe Gitlab::GithubImport::Representation::DiffNote do
         html_url: 'https://github.com/foo/bar/pull/42',
         path: 'README.md',
         commit_id: '123abc',
+        original_commit_id: 'original123abc',
         diff_hunk: hunk,
         user: double(:user, id: 4, login: 'alice'),
         body: 'Hello world',
@@ -99,6 +100,7 @@ RSpec.describe Gitlab::GithubImport::Representation::DiffNote do
           'noteable_id' => 42,
           'file_path' => 'README.md',
           'commit_id' => '123abc',
+          'original_commit_id' => 'original123abc',
           'diff_hunk' => hunk,
           'author' => { 'id' => 4, 'login' => 'alice' },
           'note' => 'Hello world',
@@ -117,6 +119,7 @@ RSpec.describe Gitlab::GithubImport::Representation::DiffNote do
         'noteable_id' => 42,
         'file_path' => 'README.md',
         'commit_id' => '123abc',
+        'original_commit_id' => 'original123abc',
         'diff_hunk' => hunk,
         'note' => 'Hello world',
         'created_at' => created_at.to_s,
@@ -145,6 +148,7 @@ RSpec.describe Gitlab::GithubImport::Representation::DiffNote do
         'noteable_id' => 42,
         'file_path' => 'README.md',
         'commit_id' => '123abc',
+        'original_commit_id' => 'original123abc',
         'diff_hunk' => hunk,
         'author' => { 'id' => 4, 'login' => 'alice' },
         'note' => 'Hello world',