Expand diffs that contain comments by default

src/api/app/components/diff_list_component.html.haml

@@ -1,6 +1,6 @@
 - diff_list.each_with_index do |(name, file_info), file_index|
   - state = file_info['state']
-  - expanded = expand?(name, state)
+  - expanded = expand?(name, state, file_index)
   .accordion.mb-2{ id: "diff-list-#{name.parameterize}" }
     .accordion-item
       %h2.accordion-header

src/api/app/components/diff_list_component.rb

@@ -11,7 +11,17 @@ def initialize(diff_list:, view_id: nil, commentable: nil)
     @commented_lines = commentable ? commentable.comments.where.not(diff_ref: nil).select(:diff_ref).distinct.pluck(:diff_ref) : []
   end
 
-  def expand?(filename, state)
-    state != 'deleted' && filename.exclude?('/') && (filename == '_patchinfo' || filename.ends_with?('.spec', '.changes'))
+  # We expand the diff if the changeset:
+  # it's not for a deletion
+  # and it is not a directory
+  # and it's a _patchinfo, *.spec or *.changes file
+  # or someone commented on the diff
+  def expand?(filename, state, file_index)
+    return true if
+      state != 'deleted' &&
+      filename.exclude?('/') &&
+      (filename == '_patchinfo' || filename.ends_with?('.spec', '.changes'))
+
+    commented_lines.any? { |cl| cl.split('_')[1].to_i == file_index }
   end
 end