Handle git errors when cleaning up MR refs

Gitlab::Git::Repository::GitError and Gitlab::Git::CommandError
errors can get raised when trying to cleanup MR refs. This will
result to the worker being retried and move to dead queue when
failed after the retry limit.

We don't need to retry in this case as the job will be scheduled
again when picked up by `ScheduleMergeRequestCleanupRefsWorker`
that runs every minute via sidekiq cron.

app/services/merge_requests/cleanup_refs_service.rb

@@ -36,6 +36,8 @@ module MergeRequests
       return error('Failed to update schedule.') unless update_schedule
 
       success
+    rescue Gitlab::Git::Repository::GitError, Gitlab::Git::CommandError => e
+      error(e.message)
     end
 
     private

changelogs/unreleased/pb-handle-git-errors-cleanup-refs.yml

+---
+title: Handle git errors when cleaning up MR refs
+merge_request: 50250
+author:
+type: fixed

spec/services/merge_requests/cleanup_refs_service_spec.rb

@@ -91,6 +91,26 @@ RSpec.describe MergeRequests::CleanupRefsService do
         it_behaves_like 'service that does not clean up merge request refs'
       end
 
+      context 'when a git error is raised' do
+        context 'Gitlab::Git::Repository::GitError' do
+          before do
+            allow(merge_request.project.repository).to receive(:delete_refs).and_raise(Gitlab::Git::Repository::GitError)
+          end
+
+          it_behaves_like 'service that does not clean up merge request refs'
+        end
+
+        context 'Gitlab::Git::CommandError' do
+          before do
+            allow_next_instance_of(Gitlab::Git::KeepAround) do |keep_around|
+              expect(keep_around).to receive(:kept_around?).and_raise(Gitlab::Git::CommandError)
+            end
+          end
+
+          it_behaves_like 'service that does not clean up merge request refs'
+        end
+      end
+
       context 'when cleanup schedule fails to update' do
         before do
           allow(merge_request.cleanup_schedule).to receive(:update).and_return(false)