Allow commenting on individual commits inside an MR

2 files changed, 44 insertions, 14 deletions

diff --git a/app/controllers/projects/commit_controller.rb b/app/controllers/projects/commit_controller.rb
index 6ff96a3f295..2e7344b1cad 100644
--- a/app/controllers/projects/commit_controller.rb
+++ b/app/controllers/projects/commit_controller.rb
@@ -134,6 +134,23 @@ class Projects::CommitController < Projects::ApplicationController
     @grouped_diff_discussions = commit.grouped_diff_discussions
     @discussions = commit.discussions
 
+    if merge_request_iid = params[:merge_request_iid]
+      @merge_request = MergeRequestsFinder.new(current_user, project_id: @project.id).find_by(iid: merge_request_iid)
+
+      if @merge_request
+        @new_diff_note_attrs.merge!(
+          noteable_type: 'MergeRequest',
+          noteable_id: @merge_request.id
+        )
+
+        merge_request_commit_notes = @merge_request.notes.where(commit_id: @commit.id).inc_relations_for_view
+        merge_request_commit_diff_discussions = merge_request_commit_notes.grouped_diff_discussions(@commit.diff_refs)
+        @grouped_diff_discussions.merge!(merge_request_commit_diff_discussions) do |line_code, left, right|
+          left + right
+        end
+      end
+    end
+
     @notes = (@grouped_diff_discussions.values.flatten + @discussions).flat_map(&:notes)
     @notes = prepare_notes_for_rendering(@notes, @commit)
   end
diff --git a/app/controllers/projects/merge_requests/diffs_controller.rb b/app/controllers/projects/merge_requests/diffs_controller.rb
index 9f966889995..42a6e5be14f 100644
--- a/app/controllers/projects/merge_requests/diffs_controller.rb
+++ b/app/controllers/projects/merge_requests/diffs_controller.rb
@@ -20,18 +20,33 @@ class Projects::MergeRequests::DiffsController < Projects::MergeRequests::Applic
   private
 
   def define_diff_vars
+    @merge_request_diffs = @merge_request.merge_request_diffs.viewable.select_without_diff.order_id_desc
+
+    if commit_id = params[:commit_id].presence
+      @commit = @merge_request.target_project.commit(commit_id)
+      @compare = @commit
+    else
+      @compare = find_merge_request_diff_compare
+    end
+
+    return render_404 unless @compare
+
+    @diffs = @compare.diffs(diff_options)
+  end
+
+  def find_merge_request_diff_compare
     @merge_request_diff =
-      if params[:diff_id]
-        @merge_request.merge_request_diffs.viewable.find(params[:diff_id])
+      if diff_id = params[:diff_id].presence
+        @merge_request.merge_request_diffs.viewable.find_by(id: diff_id)
       else
         @merge_request.merge_request_diff
       end
 
-    @merge_request_diffs = @merge_request.merge_request_diffs.viewable.order_id_desc
+    return unless @merge_request_diff
+
     @comparable_diffs = @merge_request_diffs.select { |diff| diff.id < @merge_request_diff.id }
 
-    if params[:start_sha].present?
-      @start_sha = params[:start_sha]
+    if @start_sha = params[:start_sha].presence
       @start_version = @comparable_diffs.find { |diff| diff.head_commit_sha == @start_sha }
 
       unless @start_version
@@ -40,20 +55,18 @@ class Projects::MergeRequests::DiffsController < Projects::MergeRequests::Applic
       end
     end
 
-    @compare =
-      if @start_sha
-        @merge_request_diff.compare_with(@start_sha)
-      else
-        @merge_request_diff
-      end
-
-    @diffs = @compare.diffs(diff_options)
+    if @start_sha
+      @merge_request_diff.compare_with(@start_sha)
+    else
+      @merge_request_diff
+    end
   end
 
   def define_diff_comment_vars
     @new_diff_note_attrs = {
       noteable_type: 'MergeRequest',
-      noteable_id: @merge_request.id
+      noteable_id: @merge_request.id,
+      commit_id: @commit&.id
     }
 
     @diff_notes_disabled = false