Cannot mark a Commit as todo via `/todo`

app/services/quick_actions/interpret_service.rb

@@ -301,6 +301,7 @@ module QuickActions
     desc 'Add a todo'
     explanation 'Adds a todo.'
     condition do
+      issuable.is_a?(Issuable) &&
         issuable.persisted? &&
         !TodoService.new.todo_exist?(issuable, current_user)
     end

spec/services/quick_actions/interpret_service_spec.rb

@@ -637,16 +637,6 @@ describe QuickActions::InterpretService do
       let(:issuable) { merge_request }
     end
 
-    it_behaves_like 'todo command' do
-      let(:content) { '/todo' }
-      let(:issuable) { issue }
-    end
-
-    it_behaves_like 'todo command' do
-      let(:content) { '/todo' }
-      let(:issuable) { merge_request }
-    end
-
     it_behaves_like 'done command' do
       let(:content) { '/done' }
       let(:issuable) { issue }
@@ -796,6 +786,28 @@ describe QuickActions::InterpretService do
       let(:issuable) { issue }
     end
 
+    context '/todo' do
+      let(:content) { '/todo' }
+
+      context 'if issuable is an Issue' do
+        it_behaves_like 'todo command' do
+          let(:issuable) { issue }
+        end
+      end
+
+      context 'if issuable is a MergeRequest' do
+        it_behaves_like 'todo command' do
+          let(:issuable) { merge_request }
+        end
+      end
+
+      context 'if issuable is a Commit' do
+        it_behaves_like 'empty command' do
+          let(:issuable) { commit }
+        end
+      end
+    end
+
     context '/copy_metadata command' do
       let(:todo_label) { create(:label, project: project, title: 'To Do') }
       let(:inreview_label) { create(:label, project: project, title: 'In Review') }