Release libgit2 cache and open file descriptors after `git gc` run

Relates to #21879

app/workers/git_garbage_collect_worker.rb

@@ -44,6 +44,10 @@ class GitGarbageCollectWorker
 
     # Refresh the branch cache in case garbage collection caused a ref lookup to fail
     flush_ref_caches(project) if task == :gc
+
+    # In case pack files are deleted, release libgit2 cache and open file
+    # descriptors ASAP instead of waiting for Ruby garbage collection
+    project.cleanup
   ensure
     cancel_lease(lease_key, lease_uuid) if lease_key.present? && lease_uuid.present?
   end

changelogs/unreleased/sh-cleanup-after-git-gc.yml

+---
+title: Release libgit2 cache and open file descriptors after `git gc` run
+merge_request:
+author:
+type: fixed

spec/workers/git_garbage_collect_worker_spec.rb

@@ -195,6 +195,12 @@ describe GitGarbageCollectWorker do
 
         expect(File.exist?(bitmap_path(after_packs.first))).to eq(bitmaps_enabled)
       end
+
+      it 'cleans up repository after finishing' do
+        expect_any_instance_of(Project).to receive(:cleanup).and_call_original
+
+        subject.perform(project.id, 'gc', lease_key, lease_uuid)
+      end
     end
 
     context 'with bitmaps enabled' do