Don't show image diff note on text file

changelogs/unreleased/58808-fix-image-diff-on-text.yml

+---
+title: Don't show image diff note on text file
+merge_request: 30221
+author:
+type: fixed

lib/gitlab/diff/lines_unfolder.rb

@@ -54,7 +54,7 @@ module Gitlab
       def unfold_required?
         strong_memoize(:unfold_required) do
           next false unless @diff_file.text?
-          next false unless @position.unchanged?
+          next false unless @position.on_text? && @position.unchanged?
           next false if @diff_file.new_file? || @diff_file.deleted_file?
           next false unless @position.old_line
           # Invalid position (MR import scenario)

spec/lib/gitlab/diff/lines_unfolder_spec.rb

@@ -842,4 +842,37 @@ describe Gitlab::Diff::LinesUnfolder do
       end
     end
   end
+
+  context 'positioned on an image' do
+    let(:position) do
+      Gitlab::Diff::Position.new(
+        base_sha: '1c59dfa64afbea8c721bb09a06a9d326c952ea19',
+        start_sha: '1c59dfa64afbea8c721bb09a06a9d326c952ea19',
+        head_sha: '1487062132228de836236c522fe52fed4980a46c',
+        old_path: 'image.jpg',
+        new_path: 'image.jpg',
+        position_type: 'image'
+      )
+    end
+
+    before do
+      allow(old_blob).to receive(:binary?).and_return(binary?)
+    end
+
+    context 'diff file is not text' do
+      let(:binary?) { true }
+
+      it 'returns nil' do
+        expect(subject.unfolded_diff_lines).to be_nil
+      end
+    end
+
+    context 'diff file is text' do
+      let(:binary?) { false }
+
+      it 'returns nil' do
+        expect(subject.unfolded_diff_lines).to be_nil
+      end
+    end
+  end
 end